MAPSview
MAPSview Data Descriptions
- Key Parameter data set is governed by the MAPS Rules-of-the-Road and by the Cassini Rules-of-the-Road as is all MAPS data.
- Key Parameter data should be considered browse quality. For more information about the data consult the following references.
The purpose of the MAPS Key Parameters (MKP) is to facilitate interdisciplinary science by allowing Cassini MAPS scientists easy access to MAPS instrument data. The data will be accessible soon after downlink in order to allow the following scientific investigations:
- First cut scoping of ideas and the data
- searching for events and coincidences of events by more than one instrument
- event studies and statistical studies.
By design, the MKP data set is not optimized for the study of targeted flybys of Titan or the icy satellites since these data sets will be more varied in makeup.
Please note that only Key Parameter data is available from this site. The Key Parameters have been designed to provide a first look at the plasma and fields environment at Saturn. The intended uses of the data include first cut scoping of ideas and searching for events and coincidences of events by more than one instrument. More comprehensive data or data from other instruments should be obtained from the instrument PIs directly.
MISSION.CAT:
PDS_VERSION_ID = PDS3
RECORD_TYPE = STREAM
LABEL_REVISION_NOTE = "
2003-02-20 CASSINI: conner Revision 1;
2003-03-06 PDS/RS: simpson Revision 2;
2003-03-18 CASSINI: conner Revision 3;
2003-03-20 PDS/RS: simpson Revision 4;
2003-03-21 CASSINI conner Revision 5;
2003-03-24 CASSINI conner Revision 6;
2003-04-21 CASSINI conner Revision 7;
2003-06-23 CASSINI conner Revision 8
2003-07-01 PDS/CN: S.L. Adams, formatted for ingestion from WORD
to ASCII of 'Revision 8' supplied
by Diane Conner.
2003-07-14 CASSINI conner, corrected spelling errors.
2003-09-22 CASSINI conner, added Solar System target.
2003-10-03 CASSINI conner, removed extra spaces at beg of line.
2003-10-16 CASSINI conner, changed to SOLAR_SYSTEM."
OBJECT = MISSION
MISSION_NAME = "CASSINI-HUYGENS"
OBJECT = MISSION_INFORMATION
MISSION_START_DATE = 1997-10-15
MISSION_STOP_DATE = NULL
MISSION_ALIAS_NAME = { "CASSINI", "HUYGENS" }
MISSION_DESC = "
The majority of the text in this file was extracted from the Cassini
Mission Plan Document, D. Seal, 2003. (JPLD-5564)
The Cassini spacecraft, including the Huygens Probe, was launched on 15
October 1997 using a Titan IV/B launch vehicle with Solid Rocket Motor
Upgrade (SRMU) strap-ons and a Centaur upper stage. The spacecraft used a
6.7-year Venus-Venus-Earth-Jupiter Gravity Assist (VVEJGA) trajectory to
Saturn, during which cruise observations were conducted to check out,
calibrate, and maintain the instruments as well as to perform limited
science. After Saturn Orbit Insertion (SOI) (1 July 2004), the Huygens
Probe separated and, on the third encounter with Titan, entered the
satellite's atmosphere to make in situ measurements during an approximately
150 minute descent (14 January 2005). The Orbiter continued a tour of the
Saturn system until mid-2008 collecting data on the planet and its
satellites, rings, and environment.
The Cassini Orbiter (CO) was a three-axis stabilized spacecraft equipped
with one high gain antenna (HGA) and two low gain antennas (LGAs), three
Radioisotope Thermoelectric Generators (RTGs) for power, main engines,
attitude thrusters, and reaction wheels. It carried twelve orbiter
instruments designed to carry out 27 diverse science investigations. The
Huygens Probe (HP) was equipped with six instruments designed to study the
atmosphere and surface of Titan. It entered the upper atmosphere protected
by a heat shield, then deployed parachutes to descend slowly to the surface
from an altitude of about 200 km. The instruments, with acronym and
Principal Investigator (PI) or Team Leader (TL), are summarized below:
Instrument Acronym PI/TL
----------------------------------------------- ------------
Orbiter:
Cassini Plasma Spectrometer CAPS Young
Cosmic Dust Analyzer CDA Srama
Composite Infrared Spectrometer CIRS Flasar
Ion and Neutral Mass Spectrometer INMS Waite
Imaging Science Subsystem ISS Porco
Magnetometer MAG Dougherty
Magnetospheric Imaging Instrument MIMI Krimigis
Cassini Radar RADAR Elachi
Radio and Plasma Wave Science RPWS Gurnett
Radio Science Subsystem RSS Kliore
Ultraviolet Imaging Spectrograph UVIS Esposito
Visible and Infrared Mapping Spectrometer VIMS Brown
Probe:
Aerosol Collector and Pyrolyser ACP Israel
Descent Imager Spectral Radiometer DISR Tomasko
Doppler Wind Experiment DWE Bird
Gas Chromatograph Mass Spectrometer GCMS Niemann
Huygens Atmospheric Structure Instrument HASI Fulchignoni
Surface Science Package SSP Zarnecki
Mission Phases
==============
LAUNCH 1997-10-15 to 1997-10-17
1997-288 to 1997-290
------
Cassini successfully lifted-off from the Cape Canaveral Air Station complex
40 on 15 October 1997 at 08:55 UTC. The solid rocket motors burned from
liftoff to separation at 2 min 23 sec at an altitude of 68,300 m. Stage 1
ignition began at 2 min 11 sec at an altitude of 58,500 m, and Stage 2
ignition (and Stage 1 separation) occurred at 5 min 23 sec after liftoff at
167,300 m. During the first three minutes and 27 seconds of flight, the
payload fairing shrouded the spacecraft, protecting it from direct solar
illumination.
The Centaur upper stage separated from the launch vehicle at 9 min 13 sec
at 206,700 m. The first Centaur burn began at 9 min 13 sec and lasted
approximately two minutes. This burn placed the Cassini spacecraft into an
elliptical, 170 km by 445 km parking orbit with an inclination of about 30
degrees. After 17 minutes in the parking orbit, the Centaur fired again and
launched Cassini toward Venus en route to Saturn. The injection C3 was 16.6
km^2/s^2.
Immediately after separation from the Centaur (date?), the spacecraft's
Attitude and Articulation Control Subsystem (AACS) pointed the HGA toward
the Sun to achieve a thermally safe attitude in which the HGA served as an
umbrella for the remainder of the spacecraft. X-band uplink and downlink
was established through the LGAs, the Radio and Plasma Wave Science (RPWS)
Langmuir Probe was deployed, instrument replacement heaters and main engine
oxidizer valve heaters were turned on, and the Stellar Reference Unit
(SRU), Imaging Science Subsystem (ISS), and Visible and Infrared Mapping
Spectrometer (VIMS) decontaminations were started.
TCM 1 1997-10-18 to 1997-11-14
1997-291 to 1997-318
-----
The Trajectory Correction Maneuver 1 (TCM 1) phase comprised four one-week
sequences. During most of the TCM 1 phase, the spacecraft was in a
relatively quiescent state with the HGA pointed toward the Sun. Telemetry
downlinked by the spacecraft was utilized to make an initial
characterization of the spacecraft and to assess whether its various
subsystems survived the launch. Deployment, decontamination, tank heating,
and AACS checkout activities were started.
Before the maneuver itself, the fuel and oxidizer tanks were heated in
order to avoid an irreversible overpressure in the propellant lines. If
the tanks fully pressurized before the spacecraft passed through the peak
temperature regime, then (when the spacecraft did enter the maximum thermal
environment) the tank pressure would climb without there being a way to
bring it back down, possibly causing an overpressure.
TCM 1 was an Earth injection clean-up maneuver placed at 25 days after
launch. TCM 1 was executed using the main engine with a delta-V magnitude
of 2.8 m/s. The burn sequence included holding the spacecraft off-Sun after
burn completion to allow the spacecraft heating to be characterized in a
relatively benign environment.
INTERPLANETARY CRUISE 1997-11-14 to 1999-11-07
1997-318 to 1999-311
---------------------
The Interplanetary Cruise Phase extended from 14 November 1997 to 7
November 1999. It consisted of three subphases: Venus 1 Cruise,
Instrument Checkout 1, and Venus 2 - Earth Cruise. During most of this
phase, Cassini's proximity to the Sun constrained the spacecraft to remain
Sun-pointed, and communications were conducted using the Low Gain Antennas.
The downlink capability of the LGAs at large spacecraft-Earth ranges was
very limited. Between 30 and 150 days after launch, for example, the
downlink data rate decreased from 948 to 20 bps.
Beginning on 28 December 1998, the spacecraft approached opposition and the
HGA could be pointed towards Earth for a period of 25 days while the Probe
equipment temperature remained within the required range. This provided a
high data rate window during which checkout activities could be
accomplished.
VENUS 1 CRUISE 1997-11-14 to 1998-09-13
1997-318 to 1998-256
--------------
The Venus 1 Cruise subphase started on 14 November 1997 and continued
through 13 September 1998. The subphase encompassed sequences C5 through C9
and included two TCMs, one planetary swingby, and three switches between
LGA1 and LGA2. Most of the period was dedicated to engineering and
instrument maintenance activities.
VENUS 1 ENCOUNTER 1998-04-26
1998-116
The first Venus encounter occurred on 26 April 1998. The spacecraft
approached Venus from a sunward direction, and closest approach occurred
just after the spacecraft entered the Sun's shadow for a period of about 15
minutes. At closest approach, the altitude was 284 km, with a velocity
relative to Venus of 11.8 km/s. The spacecraft was occulted from Earth for
about 2 hours. The Earth occultation zone started about 15 minutes after
the spacecraft left the Sun occultation zone. Accuracy for the Venus flyby
was assured by using two TCMs (Trajectory Correction Maneuvers), 60 and 20
days before closest approach, and a clean-up maneuver 20 days after the
flyby.
INSTRUMENT CHECKOUT 1 1998-09-14 to 1999-03-14
1998-257 to 1999-073
---------------------
The Instrument Checkout 1 subphase (ICO-1) started on 14 September 1998,
continued through 14 March 1999, and consisted of sequences C10-C13. This
subphase was characterized by the opposition that occurred on 9 January
1999, which allowed use of the HGA for downlink since the Earth and Sun
were nearly aligned as seen from Cassini.
All instruments scheduled checkout activities within the 25 day period
centered on opposition. This was the first opportunity since launch to
exercise and check the status of most instruments outside of routine
maintenance. The 'Quiet Test', for example, allowed each instrument to
monitor other instruments as they turned on and off and provided valuable
insight into how to integrate science observations during the Saturn tour.
During instrument checkout activities, the spacecraft autonomously went
into a safe state. Accumulating star position errors from the slow turn
required to keep the Sun on the -x-axis triggered AACS fault protection.
Most of the instrument checkout activities were rescheduled after a 10 day
safing period. Those that were not completed were rescheduled for the ICO-2
subphase during Outer Cruise.
VENUS 2 - EARTH CRUISE 1999-03-15 to 1999-11-07
1999-074 to 1999-311
----------------------
The Venus 2 - Earth Cruise subphase started on 15 March 1999, 45 days prior
to the second Venus flyby, and continued through 7 November 1999, which was
82 days after the Earth flyby. The subphase encompassed sequences C13
through C16, and included seven scheduled TCMs, two planetary swingbys, and
25 science activities in addition to normal engineering activities. Science
activities included maintenance, calibration, checkout, and science
observations using all of the Cassini instruments except INMS and CIRS.
VENUS 2 ENCOUNTER 1999-06-24
1999-175
TCM-7 was executed 37 days before the Venus 2 Encounter. TCM-8 was
scheduled 21 days prior to Venus 2, but it was canceled. DSN (Deep Space
Network) coverage increased from one to three passes per day in support of
the flyby.
EARTH ENCOUNTER 1999-08-18
1999-230
The Earth flyby occurred 55 days after the Venus 2 flyby. The spacecraft
approached the Earth from approximately the direction of the Sun. Closest
approach occurred right after the spacecraft entered the Sun occultation
zone. The occultation lasted approximately 30 minutes. The altitude at
closest approach was 1175 km, with an Earth-relative velocity of 19.0 km/s.
Trajectory correction maneuvers took place 43, 30, 15 and 6.5 days before
closest approach, and a clean-up maneuver was executed 13 days after the
flyby. Continuous DSN coverage began at the Venus 2 flyby and continued
through the Earth flyby. A week after the Earth Encounter, DSN coverage
dropped to one pass every two days.
Five instruments conducted observations as Cassini passed through the
Earth's magnetotail.
OUTER CRUISE 1999-11-08 to 2002-07-07
1999-312 to 2002-188
------------
The Outer Cruise Phase consisted of four subphases: HGA Transition,
Instrument Checkout 2, Jupiter Cruise, and Quiet Cruise. The Outer Cruise
phase extended from 8 November 1999 (when the spacecraft reached a Sun
range of 2.7 AU) to 7 July 2002 (about two years before Saturn Orbit
Insertion). At 2.7 AU (1 February 2000), the HGA began continuous Earth-
pointing. The one planetary encounter in this phase was the flyby of
Jupiter in December 2000. Science at Jupiter was an opportunity to test
Saturn observation strategies with HGA data rates.
HIGH GAIN ANTENNA TRANSITION 1999-11-08 to 2000-05-06
1999-312 to 2000-127
----------------------------
This subphase included sequences C17 to C19, operation of ISS and VIMS
decontamination heaters, CDA dust calibrations, and Magnetosphere and
Plasma Science (MAPS) observations after the HGA was pointed toward Earth.
During the initial part of the subphase (C17 and part of C18),
telecommunications were via LGA1, and the spacecraft was at the farthest
distance from Earth before transitioning to the HGA for regular use.
Therefore, data rates were very low and activities were kept to a minimum.
C17 included standard maintenance and one Periodic Engineering Maintenance
(PEM) activity. Activities during the LGA1 portion of C18 included a
Periodic Instrument Maintenance (PIM); observations by ISS, VIMS, and UVIS
of the asteroid Masursky near closest approach (1,634,000 km); and ISS dark
frame calibration images directly following the Masursky observations.
The HGA was turned toward Earth for regular use on 1 February 2000, during
C18. Several activities took place during the rest of C18, using the
greater telemetry capabilities available with the HGA: playback of the
Masursky data and ISS dark frames, a Probe checkout, a Huygens Probe S-band
Relay to Cassini Test, a Telemetry-Ranging Interference Test, MAG
calibrations, and a PEM. Regular MAPS observations by CAPS, CDA, MAG, MIMI,
and RPWS began within a few days after transitioning to the HGA.
The first 6 weeks of C19 were used for a checkout of new Flight Software.
The AACS version A7 software was uploaded near the beginning of this
period, and the first 2 weeks were devoted to AACS tests. The next 4 weeks
were originally scheduled for CDS tests of version V7.0. However, these
tests were delayed to late July and August of 2000 to allow time for
additional regression testing. During the AACS checkout period, MAPS
activity ceased. Several activities took place during the last 3 weeks of
C19: resumption of MAPS observations, three RSS activities (HGA pattern
calibration, HGA boresight calibration, and USO characterization), CIRS
Cooler Cover release, and a PIM.
A few days before the end of C19, the command loss timer setting was
increased slightly, to account for the 10-day period at the beginning of
C20 during which superior conjunction made commanding problematic.
INSTRUMENT CHECKOUT 2 2000-05-06 to 2000-11-05
2000-127 to 2000-310
---------------------
The second instrument checkout subphase (ICO-2) was scheduled from 6 May
2000 to 5 November of 2000, after the Spacecraft Office had completed its
engineering checkout activities. ICO-2 included instrument checkout that
required reaction wheel stability and any instrument checkouts that were
not successfully completed during ICO-1. But the CDS Flight Software V7
uplink and checkout, which was delayed from March, was rescheduled to late
July through early September 2000, causing many ICO-2 activities to be
compressed into a shorter and more intense period. Some activities were
postponed until after the Jupiter observations were completed in 2001.
The subphase began with a superior conjunction which precluded early
science or engineering activities. MAPS instruments remained on; but data
return was not attempted during conjunction. Two TCMs were scheduled for
Jupiter targeting, in June and September.
Engineering activities included the continuous use of reaction wheels and,
beginning on 1 October 2000, dual Solid State Recorders (SSRs). There were
no scheduled instrument PIMs during ICO-2 since all instruments had other
activities that accomplished this function. Other engineering activities
included two Reaction Wheel Assembly (RWA) friction tests, two PEMs, and an
SRU calibration.
Science activities began with the MAPS instruments continuing from C19. New
flight software was loaded for eight instruments in late May, and a CDA
software update was done in September. New Quiet Tests, while operating on
reaction wheels, were done in July for most instruments. RSS Quiet Tests
were done in September, and RADAR related tests were done in late June. A
Probe checkout occurred in late July.
Spacecraft turns were done for RADAR observations of the Sun and Jupiter in
June and again in September. The star Alpha Piscis Austrinus (Fomalhaut)
was also observed in September by VIMS with ISS and UVIS doing ride-along
science. No other science turns were scheduled until October. On 1 October,
science began using a repeating 5-day template to gather Jupiter science.
This involved 11 turns in a 5 day period, including two downlinks. The
turns in the 5-day template involved 4 orientations:
Orbiter Remote Science (ORS) boresights to Jupiter,
Z axis parallel to ecliptic
HGA to Sun, rolling about Z axis
Probe to Sun, rotating about X axis
HGA to Earth, Probe offset from Sun for CDA, not
rotating, downlink orientation
JUPITER CRUISE 2000-11-05 to 2001-04-30
2000-310 to 2001-120
--------------
The Jupiter Cruise subphase extended from 6 November 2000 to 29 April 2001
and included sequences C23 to C25. However Jupiter remote sensing
observations actually began on 1 October 2000, in C22.
JUPITER ENCOUNTER 2000-12-30
2000-365
The Jupiter flyby occurred on 30 December 2000 at an altitude of 9.7
million km. This gravity assist rotated the trajectory 12 deg and increased
the heliocentric velocity by 2 km/s. The Jupiter relative speed at closest
approach was 11.6 km/s. At closest approach, Jupiter filled the Narrow
Angle Camera (NAC) field of view. Extensive Jupiter science was performed
which required additional DSN support: up to two passes every five days,
and a maximum of one pass every 30 hours in the 10 days on either side of
closest approach. Science at Jupiter was an opportunity to test how to
build and execute viable Saturn sequences.
A problem with the RWAs occurred on 16 December 2000. Increased friction on
one of the wheels caused the spacecraft to switch autonomously to the
Reaction Control Subsystem (RCS) for attitude control. With the switch to
RCS, hydrazine usage increased. Two of four joint CAPS-Hubble Space
Telescope observations, a Jupiter North-South map, the Himalia 'flyby', and
a UVIS torus observation were all executed on RCS before the sequence was
terminated on 19 December 2000. MAPS data continued to be recorded at a
reduced rate. All other planned science activities were suspended. After
tests, RWA operation was resumed for attitude control on 22 December, with
the wheels biased away from low RPM regions. The sequence was restarted on
29 December.
QUIET CRUISE 2001-04-30 to 2002-07-08
2001-120 to 2002-189
------------
Quiet Cruise was a 14 month subphase that started at the end of Jupiter
Cruise and ended two years before SOI. During this subphase, routine
maintenance, engineering, and navigation functions were carried out. One
Gravitational Wave Experiment (GWE) was conducted in December 2001, and one
Solar Conjunction Experiment (SCE) was conducted in June 2002.
SCIENCE CRUISE 2002-07-08 to 2004-06-10
2002-189 to 2004-162
--------------
SPACE SCIENCE 2002-07-08 to 2004-01-11
2002-189 to 2004-011
The Space Science subphase began on 8 July 2002 and ran through 11 January
2004. TCMs 18 and 19, two GWEs (December 2002 and December 2003) and one
SCE (June-July 2003) were conducted.
APPROACH SCIENCE 2004-01-12 to 2004-06-10
2004-012 to 2004-162
The Approach Science subphase began six months before SOI and ended three
weeks before SOI, when the spacecraft was approaching Saturn at a rate of 5
kilometers per second. Most of the activities during the Approach Science
subphase were Saturn science observations and preparation for the Phoebe
flyby, SOI, and Tour operations.
The reaction wheels were turned on at the beginning of the subphase to
provide a more stable viewing platform. By this point, the imaging
instruments had begun atmospheric imaging, and making long-term atmospheric
movies. CIRS began long integrations of Saturn's disk. At SOI - 4 months,
Saturn filled one third of the NAC field of view and one half of the CIRS
Far Infrared (FIR) field of view.
The Saturn approach was made toward the morning terminator at a phase angle
of about 75 degrees; VIMS gathered data on the temperature difference
across the terminator. UVIS scans of the Saturn System began 3-4 months
before SOI. Fields, particles, and waves instruments collected solar wind
information and recorded Saturn emissions as the spacecraft neared the
planet. Science data gathered during this period was stored on the SSR and
transmitted back to Earth. Daily DSN tracking coverage began 90 days before
SOI.
The Phoebe approach TCM took place on 27 May 2004, 15 days before Phoebe
closest approach.
TOUR PRE-HUYGENS 2004-06-11 to 2004-12-24
2004-163 to 2004-359
----------------
The Tour Pre-Huygens Phase extended from the Phoebe Encounter through
Saturn Orbit Insertion to separation of the Huygens Probe from the Cassini
Orbiter.
PHOEBE ENCOUNTER 2004-06-11
2004-163
The flyby of Phoebe occurred on 11 June 2004, 19 days before SOI. At
closest approach (19:33 UTC) the spacecraft was 2000 km above the surface.
SATURN ORBIT INSERTION 2004-07-01
2004-183
During Saturn Orbit Insertion (SOI) on 1 July 2004, the spacecraft made its
closest approach to the planet's surface during the entire mission at an
altitude of only 0.3 Saturn radii (18,000 km). Due to this unique
opportunity, the approximately 95-minute SOI burn (633 m/s total delta-V),
required to place Cassini in orbit around Saturn, was executed earlier than
its optimal point centered around periapsis, and instead ended near
periapsis, allowing science observations immediately after burn completion.
The SOI maneuver placed the spacecraft in an initial orbit with a periapsis
radius of 1.3 Rs, a period of 148 days, and an inclination of 16.8 degrees.
After the burn, the spacecraft was turned to allow the ORS instruments to
view the Saturn inner rings that were not in shadow. After periapsis, the
trajectory just grazed the occultation zones behind the planet with the
Earth and Sun being occulted by Saturn. After communication with Earth was
re-established, the spacecraft remained on Earth pointed for nine hours to
play back engineering and science data and to give ground personnel time to
evaluate the spacecraft status.
After SOI a pair of cleanup maneuvers was used to correct for errors in the
SOI burn. The first was immediately before superior conjunction, at SOI + 3
days, and the second was after conjunction at SOI + 16 days.
Probe checkouts were scheduled at SOI + 14 days, Probe Release Maneuver
(PRM) + 4 days, and ten days before separation.
The partial orbit between SOI and the first apoapsis was designated orbit
0. The next three orbits were designated a, b, and c.
TITAN A ENCOUNTER 2004-10-26
2004-300
TITAN B ENCOUNTER 2004-12-13
2004-348
HUYGENS DESCENT 2004-12-24 to 2005-01-14
2004-359 to 2005-014
---------------
HUYGENS PROBE SEPARATION 2004-12-24
2004-359
The probe was released from the Orbiter on 24 December 2004, 11 days after
the second Titan flyby (orbit b). Two days after the Probe was released,
the Orbiter executed a deflection maneuver to place itself on the proper
trajectory for the third encounter.
TITAN C HUYGENS 2005-01-14
2005-014
During the third flyby (orbit c), on 14 January 2005, the Huygens Probe
transmitted data to the orbiter for approximately 150 minutes during its
descent through the atmosphere to the surface.
Because the Orbiter was looking at Titan through most of the corresponding
Goldstone tracking pass, DSN support on this day was primarily through the
70-meter antennas at the Canberra and Madrid tracking complexes. While
approaching Titan, the Orbiter made its last downlink transmission (to the
Madrid station, DSS 63) before switching to Probe relay mode. The Orbiter
then turned nearly 180 degrees to point its HGA at the predicted Probe
impact point, and the Probe Support Avionics (PSA) were configured to
receive data from the Probe. Some Orbiter instruments were put into a low
power state to provide additional power for the PSA. The data from the
Probe were transmitted at S band in two separate data streams, and both
were recorded on each SSR. Following completion of the predicted descent
(maximum 150 minutes), the Orbiter listened for Probe signals for an
additional 30 minutes, in case they continued after landing.
When data collection from the Probe was completed, those data were write
protected on each SSR. The spacecraft then turned to view Titan with
optical remote sensing instruments until about one hour after closest
approach for a total observing window of TBD.
The Orbiter then turned the HGA towards Earth and began transmitting the
recorded Probe data to the Canberra 70-m antenna. The complete, four-fold
redundant set of Probe data was transmitted twice, and its receipt
verified, before the write protection on that portion of the SSR was lifted
by ground command. A second playback, including all of the Probe data and
the Orbiter instrument observations, was returned over the subsequent
Madrid 70-meter tracking pass, which was longer and at higher elevation
angles.
TOUR 2005-01-14 to 2008-06-30
2005-014 to 2008-182
----
The Tour Phase of the mission began at completion of the Huygens Probe and
Orbiter-support playback and ended on 30 June 2008. It included dozens of
satellite encounters and extended observations of Saturn, its rings, and
its environment of particles and fields.
TOUR SEQUENCE BOUNDARIES
The table below shows spacecraft background sequences, orbit revolution,
start epoch (including day-of-year in a separate column), and the length of
the sequence. For completeness, all 'S' sequences are listed even though
the first seven covered times before the Tour phase. Each orbit about
Saturn was assigned a revolution identifier starting with a, b, and c, and
then numerically ascending from 3 to 74; these were not synchronous with
sequences, some of which covered only partial orbits. Full orbits began
and ended at apoapsis; the partial orbit from SOI to the first apoapsis was
orbit 0.
Sequence Rev Epoch (SCET) DOY Duration
In days
-------- --- ----------------- --- --------
S1 - 2004-May-15 00:00 136 35
S2 0 2004-Jun-19 01:38 171 42
S3 0 2004-Jul-30 23:05 212 43
S4 a 2004-Sep-11 19:10 255 35
S5 a 2004-Oct-16 18:40 290 28
S6 a 2004-Nov-13 16:59 318 33
S7 b 2004-Dec-16 15:03 351 37
S8 c 2005-Jan-22 10:38 022 36
S9 3 2005-Feb-27 00:36 058 41
S10 6 2005-Apr-09 05:15 099 35
S11 8 2005-May-14 02:50 134 35
S12 10 2005-Jun-18 01:34 169 42
S13 12 2005-Jul-29 22:36 210 32
S14 14 2005-Aug-30 21:53 242 39
S15 16 2005-Oct-08 15:57 281 35
S16 17 2005-Nov-12 17:01 316 35
S17 19 2005-Dec-17 14:21 351 42
S18 20 2006-Jan-28 11:23 028 42
S19 22 2006-Mar-11 00:35 070 42
S20 23 2006-Apr-22 05:15 112 42
S21 24 2006-Jun-03 02:39 154 42
S22 26 2006-Jul-15 00:06 196 35
S23 27 2006-Aug-18 22:06 230 39
S24 29 2006-Sep-26 19:53 269 26
S25 31 2006-Oct-22 18:26 295 33
S26 33 2006-Nov-24 16:30 328 42
S27 36 2007-Jan-05 13:50 005 43
S28 39 2007-Feb-17 10:52 048 40
S29 41 2007-Mar-29 08:04 088 37
S30 44 2007-May-04 22:00 124 37
S31 46 2007-Jun-11 03:10 162 33
S32 48 2007-Jul-14 01:06 195 29
S33 49 2007-Aug-11 23:20 223 42
S34 50 2007-Sep-22 20:51 265 40
S35 51 2007-Nov-01 18:40 305 42
S36 54 2007-Dec-13 16:15 347 39
S37 56 2008-Jan-21 13:35 021 26
S38 59 2008-Feb-16 11:51 047 36
S39 62 2008-Mar-23 01:50 083 27
S40 65 2008-Apr-19 07:18 110 42
S41 70 2008-May-31 04:27 152 35
SATELLITE ENCOUNTER SUMMARY
This table summarizes the Cassini Orbiter satellite encounters; for
completeness, all recognized encounters are included even though the first
eight preceded the Tour phase. Rev identifies the orbit revolution as
defined above. The three character ID for the encounter is in the second
column; an appended asterisk (*) denotes a non-targeted encounter. The
target, date and time, and day-of-year are in the next three columns.
Altitude above the surface at closest approach, sense of the encounter
(whether on the inbound or outbound leg of an orbit), relative velocity at
closest approach, and phase angle at closest approach round out the
columns.
Rev Name Satellite Epoch (SCET) DOY Alt in/ Speed Phase
km out km/s deg
---- ----- --------- ---------------- --- --- --- ----- ----
0 0PH Phoebe 2004-Jun-11 19:33 163 1997 in 6.4 25
0 0MI* Mimas 2004-Jul-01 00:30 183 76424 in 22.3 80
0 0TI* Titan 2004-Jul-02 09:30 184 338958 out 8.3 67
a aTI Titan 2004-Oct-26 15:30 300 1200 in 6.1 91
b bTI Titan 2004-Dec-13 11:37 348 2358 in 6 98
b bDI* Dione 2004-Dec-15 02:11 350 81592 in 5.3 93
c cIA* Iapetus 2005-Jan-01 01:28 001 64907 in 2.1 106
c cTI Titan 2005-Jan-14 11:04 014 60000 in 5.4 93
3 3TI Titan 2005-Feb-15 06:54 046 950 in 6 102
3 3EN* Enceladus 2005-Feb-17 03:24 048 1179 out 6.6 98
4 4EN Enceladus 2005-Mar-09 09:06 068 499 in 6.6 43
4 4TE* Tethys 2005-Mar-09 11:42 068 82975 out 6.9 64
5 5EN* Enceladus 2005-Mar-29 20:20 088 63785 in 10.1 134
5 5TI Titan 2005-Mar-31 19:55 090 2523 out 5.9 65
6 6MI* Mimas 2005-Apr-15 01:20 105 77233 out 13.6 94
6 6TI Titan 2005-Apr-16 19:05 106 950 out 6.1 127
7 7TE* Tethys 2005-May-02 21:04 122 64990 in 10 118
7 7TI* Titan 2005-May-04 05:10 124 860004 out 10.2 153
8 8EN* Enceladus 2005-May-21 07:19 141 92997 out 8.1 81
9 9TI* Titan 2005-Jun-06 18:50 157 425973 in 5.8 82
10 10TI* Titan 2005-Jun-22 12:27 173 920423 in 3.7 65
11 11EN Enceladus 2005-Jul-14 19:57 195 1000 in 8.1 43
12 12MI* Mimas 2005-Aug-02 03:52 214 45112 in 6.5 83
12 12TI* Titan 2005-Aug-06 12:33 218 841452 out 3.8 62
13 13TI Titan 2005-Aug-22 08:39 234 4015 out 5.8 42
14 14TI Titan 2005-Sep-07 07:50 250 950 out 6.1 84
15 15TE* Tethys 2005-Sep-24 01:29 267 33295 out 7.7 76
15 15TI* Titan 2005-Sep-24 22:01 267 910272 out 10.7 148
15 15HY Hyperion 2005-Sep-26 01:41 269 990 out 5.6 45
16 16TI* Titan 2005-Oct-10 22:20 283 777198 in 9.7 65
16 16DI Dione 2005-Oct-11 17:58 284 500 in 9 66
16 16EN* Enceladus 2005-Oct-12 03:29 285 42635 out 6.6 75
17 17TI Titan 2005-Oct-28 03:58 301 1446 in 5.9 105
18 18RH Rhea 2005-Nov-26 22:35 330 500 in 7.3 87
19 19EN* Enceladus 2005-Dec-24 20:23 358 97169 in 6.9 133
19 19TI Titan 2005-Dec-26 18:54 360 10429 out 5.6 67
20 20TI Titan 2006-Jan-15 11:36 015 2042 in 5.8 121
21 21TI Titan 2006-Feb-27 08:20 058 1812 out 5.9 93
22 22TI Titan 2006-Mar-18 23:58 077 1947 in 5.8 148
22 22RH* Rhea 2006-Mar-21 07:01 080 85935 out 5.3 136
23 23TI Titan 2006-Apr-30 20:53 120 1853 out 5.8 121
24 24TI Titan 2006-May-20 12:13 140 1879 in 5.8 163
25 25TI Titan 2006-Jul-02 09:12 183 1911 out 5.8 148
26 26TI Titan 2006-Jul-22 00:25 203 950 in 6 105
27 27TI* Titan 2006-Aug-18 17:48 230 339190 out 4.8 121
28 28TI Titan 2006-Sep-07 20:12 250 950 in 6 45
28 28EN* Enceladus 2006-Sep-09 20:00 252 39842 out 10.3 116
29 29TI Titan 2006-Sep-23 18:52 266 950 in 6 90
30 30TI Titan 2006-Oct-09 17:23 282 950 in 6 81
31 31TI Titan 2006-Oct-25 15:51 298 950 in 6 25
32 32EN* Enceladus 2006-Nov-09 01:48 313 94410 out 14.1 27
33 33DI* Dione 2006-Nov-21 02:32 325 72293 out 12.3 144
33 33TI* Titan 2006-Nov-25 13:57 329 930525 out 4.5 114
35 35TI Titan 2006-Dec-12 11:35 346 950 in 6 124
36 36TI Titan 2006-Dec-28 10:00 362 1500 in 5.9 62
37 37TI Titan 2007-Jan-13 08:34 013 950 in 6 53
38 38TI Titan 2007-Jan-29 07:12 029 2776 in 5.8 73
39 39TI Titan 2007-Feb-22 03:10 053 953 out 6.3 161
40 40TI Titan 2007-Mar-10 01:47 069 956 out 6.3 149
41 41TI Titan 2007-Mar-26 00:21 085 953 out 6.3 144
42 42TI Titan 2007-Apr-10 22:57 100 951 out 6.3 137
43 43TI Titan 2007-Apr-26 21:32 116 951 out 6.3 130
44 44TI Titan 2007-May-12 20:08 132 950 out 6.3 121
45 45TE* Tethys 2007-May-26 20:57 146 97131 in 11.7 75
45 45TI Titan 2007-May-28 18:51 148 2425 out 6.1 114
46 46TI Titan 2007-Jun-13 17:46 164 950 out 6.3 107
47 47TE* Tethys 2007-Jun-27 19:53 178 16166 in 10.1 90
47 47MI* Mimas 2007-Jun-27 22:56 178 89730 in 16.2 110
47 47EN* Enceladus 2007-Jun-28 01:15 179 90769 out 9.4 55
47 47TI Titan 2007-Jun-29 17:05 180 1942 out 6.2 96
48 48TI Titan 2007-Jul-19 00:39 200 1302 in 6.2 34
49 49TE* Tethys 2007-Aug-29 11:21 241 48324 in 4.7 104
49 49RH* Rhea 2007-Aug-30 01:26 242 5098 out 6.7 46
49 49TI Titan 2007-Aug-31 06:34 243 3227 out 6.1 87
49 49IA Iapetus 2007-Sep-10 12:33 253 1000 out 2.4 65
50 50DI* Dione 2007-Sep-30 06:27 273 56523 in 5.6 47
50 50EN* Enceladus 2007-Sep-30 10:53 273 88174 in 6.1 99
50 50TI Titan 2007-Oct-02 04:48 275 950 out 6.3 67
51 51TI* Titan 2007-Oct-22 00:47 295 455697 in 4.1 29
52 52RH* Rhea 2007-Nov-16 19:52 320 78360 in 9.1 148
52 52TI Titan 2007-Nov-19 00:52 323 950 out 6.3 51
53 53MI* Mimas 2007-Dec-03 05:28 337 79272 in 14.8 138
53 53TI Titan 2007-Dec-05 00:06 339 1300 out 6.3 70
54 54TI Titan 2007-Dec-20 22:56 354 953 out 6.3 61
55 55TI Titan 2008-Jan-05 21:26 005 949 out 6.3 37
57 57TI* Titan 2008-Jan-22 21:06 022 860776 in 4.5 70
59 59TI Titan 2008-Feb-22 17:39 053 959 out 6.4 30
61 61TI* Titan 2008-Mar-10 19:15 070 922539 in 6.3 123
61 61EN Enceladus 2008-Mar-12 19:05 072 995 in 14.6 56
62 62TI Titan 2008-Mar-25 14:35 085 950 out 6.4 21
64 64MI* Mimas 2008-Apr-11 09:38 102 95428 in 16.9 137
66 66TI* Titan 2008-Apr-26 18:22 117 780589 in 5.5 94
67 67TI Titan 2008-May-12 10:09 133 950 out 6.4 35
69 69TI Titan 2008-May-28 08:33 149 1316 out 6.3 23
72 72TI* Titan 2008-Jun-13 04:17 165 372240 in 5.9 89
74 74EN* Enceladus 2008-Jun-30 08:07 182 99092 in 21.6 66
END OF PRIME MISSION 2008-06-30
2008-182
-------------------- "
MISSION_OBJECTIVES_SUMMARY = "
CASSINI-HUYGENS MISSION OBJECTIVES
==================================
The Cassini-Huygens mission will accomplish a variety of scientific
objectives en route to and at Saturn [PD699-004].
While en route to Saturn, Cassini performed three sets of Gravitational
Wave Experiments (GWEs), each scheduled near opposition and each lasting
approximately 40 days. During these observations, Cassini acted as a point
mass which would be perturbed by propagating gravitational waves resulting
from sudden destruction (or creation) of large masses in the general
direction of the spacecraft-to-Earth line.
While en route to Saturn, Cassini was also used in two Solar Conjunction
Experiments (SCEs), each lasting approximately 30 days. The objectives of
these observations was to test general relativity and to improve our
understanding of the solar corona.
The general scientific objectives of the Cassini mission at Saturn were to
investigate the physical, chemical, and temporal characteristics of Titan
and of Saturn, its atmosphere, rings, icy satellites, and magnetosphere.
These are listed more specifically below:
Saturn (Planet) Objectives.
--------------------------
a) Determine temperature field, cloud properties, and composition of the
atmosphere of Saturn.
b) Measure the global wind field, including wave and eddy components;
observe synoptic cloud features and processes.
c) Infer the internal structure and rotation of the deep atmosphere.
d) Study the diurnal variations and magnetic control of the ionosphere of
Saturn.
e) Provide observational constraints (gas composition, isotope ratios, heat
flux, etc.) on scenarios for the formation and the evolution of Saturn.
f) Investigate the sources and the morphology of Saturn lightning, Saturn
Electrostatic Discharges (SED), and whistlers.
Titan Objectives.
----------------
a) Determine abundance of atmospheric constituents (including any noble
gases), establish isotope ratios for abundant elements, constrain scenarios
of formation and evolution of Titan and its atmosphere.
b) Observe vertical and horizontal distributions of trace gases, search for
more complex organic molecules, investigate energy sources for atmospheric
chemistry, and model the photochemistry of the stratosphere, study
formation and composition of aerosols.
c) Measure winds and global temperatures; investigate cloud physics,
general circulation, and seasonal effects in Titan's atmosphere; search for
lightning discharges.
d) Determine the physical state, topography, and composition of the
surface; infer the internal structure of the satellite.
e) Investigate the upper atmosphere, its ionization, and its role as a
source of neutral and ionized material for magnetosphere of Saturn.
Ring Objectives.
---------------
a) Study configuration of the rings and dynamical processes (gravitational,
viscous, erosional, and electromagnetic) responsible for ring structure.
b) Map composition and size distribution of ring material.
c) Investigate interrelation of rings and satellites, including embedded
satellites.
d) Determine dust and meteoroid distribution in the vicinity of the rings.
e) Study interactions between the rings and Saturn's magnetosphere,
ionosphere, and atmosphere.
Icy Satellite Objectives.
------------------------
a) Determine the general characteristics and geological histories of the
satellites.
b) Define the mechanisms of crustal and surface modifications, both
external and internal.
c) Investigate the compositions and distributions of surface materials,
particularly dark, organic rich materials and low melting point condensed
volatiles.
d) Constrain models of the satellites' bulk compositions and internal
structures.
e) Investigate interactions with the magnetosphere and ring systems and
possible gas injections into the magnetosphere.
Magnetosphere Objectives
------------------------
a) Determine the configuration of the nearly axially symmetric magnetic
field and its relation to the modulation of Saturn Kilometric Radiation
(SKR).
b) Determine current systems, composition, sources, and sinks of
magnetosphere charged particles.
c) Investigate wave-particle interactions and dynamics of the dayside
magnetosphere and the magnetotail of Saturn and their interactions with the
solar wind, the satellites, and the rings.
d) Study the effect of Titan's interaction with the solar wind and
magnetospheric plasma.
e) Investigate interactions of Titan's atmosphere and exosphere with the
surrounding plasma. "
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TARGET_NAME = "SATURN"
END_OBJECT = MISSION_TARGET
OBJECT = MISSION_TARGET
TARGET_NAME = "TITAN"
END_OBJECT = MISSION_TARGET
OBJECT = MISSION_TARGET
TARGET_NAME = "MASURSKY"
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OBJECT = MISSION_TARGET
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OBJECT = MISSION_TARGET
TARGET_NAME = "IO"
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OBJECT = MISSION_TARGET
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OBJECT = MISSION_TARGET
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TARGET_NAME = "DIONE"
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OBJECT = MISSION_TARGET
TARGET_NAME = "EPIMETHEUS"
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OBJECT = MISSION_TARGET
TARGET_NAME = "HELENE"
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OBJECT = MISSION_TARGET
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OBJECT = MISSION_TARGET
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END_OBJECT = MISSION_TARGET
OBJECT = MISSION_TARGET
TARGET_NAME = "JANUS"
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OBJECT = MISSION_TARGET
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OBJECT = MISSION_TARGET
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OBJECT = MISSION_TARGET
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OBJECT = MISSION_TARGET
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OBJECT = MISSION_TARGET
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OBJECT = MISSION_TARGET
TARGET_NAME = "DUST"
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OBJECT = MISSION_TARGET
TARGET_NAME = "TITAN"
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END
INSTHOST.CAT:
PDS_VERSION_ID = PDS3
RECORD_TYPE = STREAM
LABEL_REVISION_NOTE = "
2003-03-24 CASSINI: conner Revision 1;
2003-04-02 PDS/RS: simpson Revision 2;
2003-04-03 CASSINI: conner Revision 3;
2003-04-16 CASSINI: conner Revision 4;
2003-04-21 CASSINI: conner Revision 5;
2003-06-23 CASSINI: conner Revision 6;
2003-07-08 CASSINI: conner Revision 7;
2003-07-08 PDS/CN: S.L.Adams Revision 7a, minor format
changes to allow ingestion.
2003-07-14 CASSINI: conner, fixed spelling errors.
2003-08-28 CASSINI: conner, Revision 8, fixed
formatting problems
found in RPWS volume review.
2003-11-17 CASSINI: conner Revision 9
fixed reference object."
OBJECT = INSTRUMENT_HOST
INSTRUMENT_HOST_ID = "CO"
OBJECT = INSTRUMENT_HOST_INFORMATION
INSTRUMENT_HOST_NAME = "CASSINI ORBITER"
INSTRUMENT_HOST_TYPE = "SPACECRAFT"
INSTRUMENT_HOST_DESC = "
The majority of the text in this file was extracted from the Cassini
Mission Plan Document, D. Seal, 2003. (JPLD-5564)
Instrument Host Overview
=========================
For most Cassini Orbiter experiments, data were collected by instruments on
the spacecraft then relayed via the orbiter telemetry system to stations of
the NASA Deep Space Network (DSN). Radio Science required the DSN for its
data acquisition on the ground. The following sections provide an
overview, first of the orbiter, then the science instruments, and
finally the DSN ground system.
Instrument Host Overview - Spacecraft
=======================================
Cassini was successfully launched on 15 October 1997 from Cape Canaveral,
Florida, using a Titan IV/Centaur launch vehicle with Solid Rocket Motor
Upgrade (SRMU) strap-ons and a Centaur upper stage. The spacecraft flew a
6.7-year Venus-Venus-Earth-Jupiter Gravity Assist (VVEJGA) trajectory to
Saturn, during which cruise operations included checkout, characterization,
calibration, and maintenance of the instruments and limited science
observations.
Until they separated after Saturn orbit insertion, Cassini was a combined
Saturn orbiter and Titan atmospheric probe. It was a three-axis stabilized
spacecraft equipped for 27 diverse science investigations with 12 orbiter
and 6 Huygens probe instruments, one high gain (HGA) and two low gain
antennas (LGAs), three Radioisotope Thermoelectric Generators (RTGs), main
engines, attitude thrusters, and reaction wheels. This description covers
the orbiter portion of Cassini, which will frequently be called 'the
spacecraft.'
Orbiter Description
===================
The Cassini orbiter was a three-axis-stabilized spacecraft. The origin of
the spacecraft coordinate system was located at the center of the plane at
the bus/upper shell structure interface (i.e., base of the electronic bays
on the upper equipment module). The remote sensing pallet was mounted on
the +X side of the spacecraft, the magnetometer boom extended in the +Y
direction, and the +Z axis completed the orthogonal body axes in the
direction of the main engine. The primary remote sensing boresights viewed
in the -Y direction, the probe was ejected in the -X direction, the HGA
boresight was in the -Z direction, the main engine exhaust was in the +Z
direction, and the main engine thrust was in the -Z direction. The
coordinates and some of the larger elements of the spacecraft are shown in
the figure below.
/\
----------------------------------
\ /
\ / HGA
\ /
MAG Boom --------------------------
... =================| |
| h |
\ ^ /
| | |
| | |
Ysc -------| v <---o |
| b, Xsc |
| |
| |
| |
| |
| |
----------------------
/ \
/ \ Main Rocket Engine
----------
|
|
|
V
Zsc
where b and Xsc point out of the screen or page.
The main body of the spacecraft was formed by a stack consisting of the
lower equipment module, the propulsion module, the upper equipment module,
and the HGA. Attached to this stack were the remote sensing pallet, the
fields and particles pallet, and the Huygens Probe system. The Huygens
Probe was built by the European Space Agency and was deployed into Titan's
atmosphere by the Orbiter. Some instruments such as RADAR and some
instrument components such as those of RPWS were attached to the upper
equipment module. The two equipment modules were also used for external
mounting of the magnetometer boom and the three radioisotope thermoelectric
generators (RTGs) which supplied the spacecraft power. The spacecraft
electronics bus was part of the upper equipment module and carried the
electronics to support the spacecraft data handling, including the command
and data subsystem and the radio frequency subsystem. Other electronics to
support instruments and other spacecraft functions were also carried in the
bus. During the inner cruise, the HGA and two Low Gain Antennas (LGAs)
were used to transmit data and receive commands. One of the two LGAs was
selected when operational constraints prevented pointing the HGA towards
the Earth.
The spacecraft stood 6.8 meters (22.3 ft) high. Its maximum diameter, the
diameter of the HGA, was 4 meters (13.1 ft). Therefore, the HGA could
fully shield the rest of the spacecraft (except the deployed MAG boom and
RPWS antennas) from sunlight when the HGA was pointed within 2.5 degrees of
the Sun. The dry mass of the spacecraft was 2523 kg, including the Huygens
Probe system and the science instruments. The best estimate of the actual
spacecraft mass at separation from the Centaur was 5573.8 kg. Future
estimates of spacecraft mass were maintained by the Spacecraft Operations
team (SCO).
SPACECRAFT SUBSYSTEMS
---------------------
The spacecraft comprised several subsystems, which are described briefly
below. For more detailed information, see JPLD-5564.
Structure Subsystem
-------------------
The Structure Subsystem (STRU) provided mechanical support and alignment
for all flight equipment including the Huygens Probe. It also served as a
local thermal reservoir and provided an equipotential container, an
electrical grounding reference, RFI shielding, and protection from
radiation and meteoroids. The STRU consisted of the Upper Equipment Module
(UEM) which contained the 12-bay electronics bus assembly, the instrument
pallets, and the MAG boom, and the Lower Equipment Module (LEM), plus all
the brackets and structure for integrating the Huygens Probe, the HGA,
LGAs, RTGs, reaction wheels, the main rocket engines, the four RCS thruster
clusters, and other equipment. The STRU also included an adapter which
supported the spacecraft on the Centaur during launch.
Radio Frequency Subsystem
-------------------------
The Radio Frequency Subsystem (RFS) provided the telecommunications
facilities for the spacecraft and was used as part of the radio science
instrument. For telecommunications, it produced an X-band carrier at 8.4
GHz, modulated it with data received from the CDS, amplified the X-band
carrier power to produce 20 W from the Traveling Wave Tube Amplifiers
(TWTA), and delivered it to the Antenna Subsystem (ANT). From ANT, RFS
accepted X-band ground command/data signals at 7.2 GHz, demodulated them,
and delivered the commands/data to CDS for storage and/or execution.
The Ultra Stable Oscillator (USO), the Deep Space Transponder (DST), the X-
band Traveling Wave Tube Amplifier (TWTA), and the X-band Diplexer were
elements of the RFS which were used as part of the radio science
instrument. The DST could phase-lock to an X-band uplink and generate a
coherent downlink carrier with a frequency translation adequate for
transmission at X-, S-, or Ka-band. The DST had the capability of
detecting ranging modulation and of modulating the X-band downlink carrier
with the detected ranging modulation. Differenced one-way ranging (DOR)
tones could also be modulated onto the downlink. The DST could also accept
the reference signal from the USO and generate a non-coherent downlink
carrier.
Propulsion Module Subsystem
---------------------------
The Propulsion Module Subsystem (PMS) provided thrust and torque to the
spacecraft. Under command from AACS, the thrust and torque established the
spacecraft attitude, pointing, and the amount of velocity vector change.
For attitude control, the PMS had a Reaction Control Subsystem (RCS)
consisting of four thruster clusters mounted off the PMS core structure
adjacent to the LEM at the base of the spacecraft. Each of the clusters
contained 4 hydrazine thrusters. The thrusters are oriented to provide
thrust along the spacecraft +/-Y and -Z axes. RCS thrusters also provide DV
for small maneuvers.
For larger DVs, the PMS had a primary and redundant pressure-regulated main
rocket engine. Each engine was capable of a thrust of approximately 445 N
when regulated. The bipropellant main engines burned nitrogen tetroxide
(N2O4) and monomethylhydrazine (N2H3CH3) producing an expected specific
impulse of up to 308s. These engines were gimbaled so when under AACS
control during burns the thrust vector could be maintained through the
shifting center of mass of the spacecraft. AACS-provided valve drivers for
all the engines/thrusters operated in response to commands received from
AACS via the CDS data bus.
Power and Pyrotechnics Subsystem
--------------------------------
The Power and Pyrotechnics Subsystem (PPS) provided regulated electrical
power from three RTGs on command from CDS to spacecraft users at 30 Volts
DC, distributed over a power bus. In addition, PPS provided power to the
various pyrotechnic devices on command from CDS. PPS disposed of excess
power by heat radiation to space via a resistance shunt radiator.
Measurements of the output of the radioisotope thermoelectric generators
indicated a beginning-of- life power of 876 +/- 6 Watts, 740 Watts at SOI,
and 692 Watts at end of mission. These estimates were at least 30 Watts
above pre-launch predictions.
Command and Data Subsystem
--------------------------
The Command and Data Subsystem (CDS) received the uplink command stream via
the RFS and decoded it. The stream included timing (immediate or
sequence), routing, action, and parameter information. The CDS then
distributed commands designated for other subsystems or instruments,
executed those commands which were decoded as CDS commands, and stored
sequence commands for later execution.
The Cassini spacecraft included two identical Solid State Recorders (SSRs).
Each CDS (A & B) was attached to the two SSRs such that each CDS could
communicate (read, write) with only one SSR at any one time. The Mission
and Science Operations Office had the capability to control how the SSR
attachments were configured via immediate command or a stored sequence.
Under fault response conditions flight software (FSW) could switch an SSR
attachment from CDS A to CDS B.
The CDS received data from other on-board subsystems via the data bus, then
processed and formatted them for telemetry and delivered them to RFS for
transmission to Earth. Each subsystem interfaced with the data bus through
a standard Bus Interface Unit (BIU) or a Remote Engineering Unit (REU).
Data were collected in 8800 bit frames, and Reed-Solomon Encoded on
downlink. A 32 framesync marker along with the encoding increased these
frames to 10,112 bits.
CDS software contained algorithms that provided protection for the
spacecraft and the mission in the event of a fault. Fault protection
software ensured that, in the case of a serious fault, the spacecraft would
be placed into a safe, stable, commandable state (without ground
intervention) for a period of at least two weeks to give the mission
operations team time to solve the problem and send the spacecraft a new
command sequence. It was also capable of autonomously responding to a
predefined set of faults needing immediate action.
Attitude and Articulation Control Subsystem
-------------------------------------------
The Attitude and Articulation Control Subsystem (AACS) provided dynamic
control of the spacecraft in rotation and translation. It provided fixed-
target staring for HGA and remote sensing pointing and performed target
relative pointing using inertial vector propagation as well as repetitive
subroutines such as scans and mosaics. AACS also controlled actuators for
the main rocket engine gimbals. Rotational motion during the Saturn tour
that required high pointing stability was normally controlled by the three
main Reaction Wheel Assemblies (RWAs), although modes requiring faster
rates or accelerations may have used thrusters. The additional fourth
reaction wheel could articulate to replace any single failed wheel.
AACS contained a suite of sensors that included redundant Sun Sensor
Assemblies (SSA), redundant Stellar Reference Units (SRU, also called star
trackers), a Z-axis accelerometer, and two 3-axis gyro Inertial Reference
Units (IRU). Each IRU consisted of four gyros, three orthogonal to each
other and the fourth skewed equidistant to the other three.
Temperature Control Subsystem
-----------------------------
The TEMPerature control subsystem (TEMP) allowed operations over the
expected solar ranges (0.61 to 10.1 AU) with some operational constraints.
Temperatures of the various parts of the spacecraft were kept within
allowable limits by a large number of local TEMP thermal control
techniques, many of which were passive. The 12-bay electronics bus had
automatically positioned reflective louvers. Radio Isotope Heater Units
(RHU) were used where constant heat input rates were needed and where
radiation was not a problem. Multilayer insulation blankets covered much
of the spacecraft and its equipment.
Electric heaters were used in different locations and operated by CDS and
instruments. Temperature sensors were located at many sites on the
spacecraft, and their measurements were used by CDS to command the TEMP
heaters. Shading was executed by pointing the HGA (-Z axis) towards the
sun; the HGA was large enough to provide shade for the entire spacecraft
body including the Huygens Probe.
Mechanical Devices Subsystem
----------------------------
The mechanical devices subsystem provided a pyrotechnic separation device
used to separate the spacecraft from the launch vehicle adapter. Springs
provided the impulse to separate the spacecraft from the adapter. The
mechanical devices subsystem also provided a self-deploying 10.5 meter
coiled longeron mast stored in a canister for the two magnetometers,
electrostatic discharge covers over inflight separation connectors, an
articulation system for the backup reaction wheel assembly, a 'pinpuller'
for the RPWS Langmuir Probe, and louvers and variable RHUs for temperature
control.
Electronic Packaging Subsystem
------------------------------
The Electronic Packaging Subsystem (EPS) consisted of the electronics
packaging for most of the spacecraft in the form of the 12-bay electronics
bus. The bus was made up of bays containing standardized, dual-shear plate
electronics modules.
Solid State Recorder Subsystem
------------------------------
Cassini's two Solid State Recorders (SSRs) were the primary memory storage
and retrieval devices used on the orbiter. Each SSR contained 128
submodules, of which 8 were used for flight software and 120 were used for
telemetry. Each submodule could hold 16,777,200 bits for data, so the
total data storage for telemetry on each SSR was 2.013 Gbits. Expressed in
terms of 8800-bit telemetry frames, this was 228,780 frames per SSR.
Spacecraft telemetry and AACS, CDS, and instrument memory loads were stored
in separate files called partitions. All data recorded to and played back
from the SSR was handled by the CDS. There were three different SSR
functional modes: Read-Write to End, Circular FIFO, and Ring Buffer. There
was also a record pointer and a playback pointer, which marked the memory
addresses at which the SSR could write or read. In Read-Write to End,
there was a logical beginning and end to the SSR. Recording began at this
logical beginning and continued until either the SSR was reset (the record
and playback pointers were returned to the logical beginning) or until the
record pointer reached the end. If the record pointer did not reach the
end, recording was halted until the SSR was reset. In Circular FIFO, there
was no logical end to the SSR. The data was continuously recorded until
the record pointer reached the playback pointer. The Ring Buffer mode
behavior was similar to the Circular FIFO except that recording did not
stop if the record pointer reached the playback pointer.
Antenna Subsystem
-----------------
The ANTenna subsystem (ANT) provided a directional high gain antenna (HGA)
with X-, Ka-, S and Ku-band for transmitting and receiving on all four
bands. Because of its narrow halfpower beam width of 0.14 deg for Ka-band,
it had to be accurately pointed. The HGA, and the low gain antenna 1
(LGA1) located on the HGA feed structure, were provided by the Italian
Space Agency. Another LGA (LGA2) was located below the Probe pointing in
the -X direction. During the inner solar system cruise, the HGA was Sun-
pointed to provide shade for the spacecraft. ANT provided two LGAs which
allowed one or the other to receive/transmit X-band from/to the Earth when
the spacecraft was Sun-pointed. The LGAs also provided an emergency
uplink/downlink capability while Cassini was at Saturn. The HGA downlink
gain at X-band was 47dBi and the LGA1 peak downlink gain was 8.9 dBi. The
X-band TWTA power was 20 watts.
ORBITER SCIENCE INSTRUMENTS
---------------------------
There were 12 science instrument subsystems on the Cassini spacecraft,
listed immediately below with their acronyms, then described in more
detail in the following paragraphs. Three of the instruments (CAPS, CDA,
and MIMI/LEMMS) were capable of commanded articulation relative to the
spacecraft.
Cassini Plasma Spectrometer CAPS
Cosmic Dust Analyzer CDA
Composite Infrared Spectrometer CIRS
Ion and Neutral Mass Spectrometer INMS
Imaging Science Subsystem ISS
Magnetometer MAG
Magnetospheric Imaging Instrument MIMI
Cassini RADAR RADAR
Radio and Plasma Wave Science RPWS
Radio Science Subsystem RSS
Ultraviolet Imaging Spectrograph UVIS
Visible and Infrared Mapping Spectrometer VIMS
Cassini Plasma Spectrometer (CAPS): The CAPS instrument was designed to
perform an in-situ study of plasma within and near Saturn's magnetosphere.
Specific science and measurement objectives were:
1) Orbital Tour Observing Objectives:
a) Near continuous survey.
b) MAPS Campaigns.
c) SOI, targeted Titan and icy satellite observations.
d) CAPS Magnetospheric Survey.
2) Solar Wind/Aurora Campaign Objectives:
a) Measure solar wind while ORS observed aurora.
b) Unambiguous measurements of unperturbed solar wind, correlation
with Earth based and RPW auroral data.
3) Study microphysical and rapidly varying processes near the bow shock and
magnetopause.
4) Observe particle acceleration, particle injection, and dynamical events
(e.g. substorms) in the magnetotail.
5) Measure vertical (field aligned) structure of plasma in the inner
magnetosphere.
6) Observe the dynamics and microphysics of the auroral and Saturn
Kilometric Radiation (SKR) source regions.
7) Study the Titan plasma torus and distant signatures of Titan's
interaction with the magnetosphere.
8) Study the distant signatures of satellites and ring interactions with
the magnetosphere.
Cosmic Dust Analyzer (CDA): The CDA instrument was designed to perform an
in- situ study of dust grains in the Saturn system. Specific science and
measurement objectives were:
1) Study interplanetary and interstellar dust at Saturn.
2) Saturn Rings Objectives:
a) Map size distribution.
b) Search for particles in the 'clear zone' (F/G ring).
c) Determine orbits of particles to identify their possible parents.
d) Study the interaction between E ring and Saturn's magnetosphere.
e) Distinguish temporal and spatial effects.
f) Analyze eccentricity and inclination of dust orbits
independently.
3) Icy Satellites Objectives:
a) Interaction with the ring system.
b) Role of satellites as a source and sink for ring particles.
c) Chemical composition of satellites (dust atmospheres).
Composite Infrared Spectrometer (CIRS): The CIRS instrument was designed to
perform spectral mapping to study temperature and composition of surfaces,
atmospheres, and rings within the Saturn system. Specific science and
measurement objectives were:
1) Thermal Structure Objectives:
a) Vertical profiles of atmospheric temperature.
b) Maps of atmospheric and surface temperatures.
c) Aerosol opacities.
d) Thermal inertia of surfaces.
e) Subsurface regolith structure.
f) Ring particle sizes.
g) Ring thermal structure.
2) Composition Objectives:
a) Spatial distribution of atmospheric gases.
b) Surfaces.
c) Ring material.
3) Atmosphere Objectives:
a) Circulation: Zonal jets, Meridional motion, vortices, wave,
convection.
b) Composition: Dis-equilibrium species, elemental and isotope
abundances and distribution, ortho/para ratio, condensable
gases, external sources (e.g., rings).
c) Clouds/Aerosols: Composition, microphysical properties, spatial
and temporal distribution.
d) Atmospheric. Structure: Temperature, pressure, density, vertical
distribution of major constituents.
e) Internal Structure: He abundance, internal heat, gravity.
f) Aurora, lighting, airglow: Spatial and temporal distribution,
special properties.
g) Titan: Aerosols and clouds, Titan winds.
4) Rings Objectives:
a) Vertical structure and thermal gradient.
b) Vertical Dynamics.
c) Particle Surface Properties.
d) Particle Composition.
e) Radial Structure.
5) Non-Targeted Icy Satellites Objectives:
a) Determine surface composition.
b) Determine vertical thermal structure (Greenhouse).
c) Determine thermophysical properties (Thermal Inertia).
d) Search for active thermal sources (space and time).
Ion and Neutral Mass Spectrometer (INMS): The INMS instrument was designed
to perform an in-situ study of the compositions of neutral and charged
particles within the Saturn magnetosphere. Specific science and
measurement objectives were:
1) Outer Magnetosphere: Science Objectives:
a) Neutral and ion composition of the magnetosphere.
b) Composition of the Titan plasma torus.
c) Additional low energy ion distribution function information to
complement CAPS.
2) Inner Magnetosphere: Science Objectives:
a) Studies of solar system formation. Plasma sources derived from
the rings and icy satellites - composition and isotopic ratio.
b) Studies of plasma transport. Determination of plasma transport
velocities and determination of momentum transfer from charge
exchange chemistry - water products.
Imaging Science Subsystem (ISS): The ISS instrument was designed to perform
multispectral imaging of Saturn, Titan, rings, and icy satellites to
observe their properties. Specific science and measurement objectives
were:
1) Motions and Dynamics:
a) Basic flow regime (Titan).
b) Poleward flux of momentum (u'v').
c) Poleward flux of heat (with CIRS).
d) Life cycles and small-scale dynamics of eddies.
e) Radiative heating for dynamical studies.
2) Clouds and Aerosols:
a) Could and haze stratigraphy (strongly couples with wind studies).
b) Particle optical properties.
c) Particle physical properties.
d) Auroral processes and particle formation.
e) Haze microphysical models.
3) Lightning (related to water clouds on Saturn, don't know what to expect
for Titan).
4) Auroras (H and H2 emissions on Saturn, N and N2 emissions on Titan).
5) ISS High Priority Rings Goals:
a) Ring Architecture/Evolution: Azimuthal, radial, temporal
variations across tour.
b) New satellites: orbits, masses/densities, effects on rings;
complete inventory of Saturn's inner moons.
c) Search and characterize material potentially hazardous to Cassini:
diffuse rings, arcs, Hill's sphere material, etc.
d) Orbit refinement of known satellites; temporal variations;
resonant effects.
e) Particle/Disk properties: vertical disk structure; particle
physical properties and size distribution; variations across disk.
f) Spokes: Formation timescales/process; periodic variations.
g) Diffuse Rings (E, G): Structure, characterize particle properties.
Magnetometer (MAG): The MAG instrument was designed to study Saturn's
magnetic field and interactions with the solar wind. Specific science and
measurement objectives were:
1) Intrinsic magnetic fields of Saturn and its moons:
a) Determine the multiple moments of Saturn's dynamo-driven
magnetic field.
b) Determine weather Titan has an internal field due to dynamo action,
electromagnetic induction or even remnant magnetization in a 'dirty
ice' crust.
c) Search for possible evidence of ancient dynamos and crustal
remnants in the icy satellites.
2) Derive a 3-D global model of the magnetospheric magnetic field.
3) Establish the relative contributions to electromagnetic and mechanical
stress balance.
4) Identify the energy source for dynamical processes (rotationally driven,
solar wind driven, or other).
5) Characterize the phenomena of the distant dayside/flank planetary
environment.
6) Survey satellite/dust/ring/torus electromagnetic interactions.
7) Determine tail structure and dynamic processes therein.
8) Establish nature and source of all ULF wave sources.
9) Magnetosphere/ionosphere coupling.
10) Titan:
a) Determine the internal magnetic field sources of Titan as well as
the sources external to I I - thereby determining the interaction
type.
b) Determine all Titan-plasma flow interactions (magnetosphere,
magnetosheath, solar wind).
c) Determine the variation of the Titan-magnetosphere interaction
with respect to Titan orbital phase.
d) Determine the nature of the low frequency wave (ion
cyclotron/hydromagnetic) spectrum of the near-Titan plasma
environment.
11) Icy Satellites:
a) Search for possible evidence of ancient dynamos and crustal
remanence in the icy satellites
b) Investigate icy satellite plasma environments.
Magnetospheric Imaging Instrument (MIMI): MIMI was designed for global
magnetospheric imaging and in-situ measurements of Saturn's magnetosphere
and solar wind interactions. Specific science and measurement objectives
were:
1) MIMI Survey:
a) What is the source of energetic particles in Saturn's magnetosphere
and how are they energized?
b) To what extent does the solar wind and rotation regulate the size,
shape and dynamics of Saturn's magnetosphere; are there Earth-like
storms and substorms?
c) How does the interaction between the magnetospheric particle
population and Saturn cause the aurora, and affect magnetospheric
and upper atmospheric processes?
d) How does the distribution of satellites affect global
magnetospheric morphology and processes?
2) MIMI Campaigns:
a) How do satellites and their exospheres affect local magnetospheric
plasma flow and contribute to energetic particle populations?
b) What particles (species, energy) cause Saturnian aurora; what
processes accelerate them and what is the exospheric response?
c) What unique role do Saturn's rings play in controlling the
structure, composition, and transport of the inner magnetosphere?
Cassini RADAR (RADAR): The RADAR instrument was designed for synthetic
aperture RADAR (SAR) imaging, altimetry, and radiometry of Titan's surface.
Specific science objectives for the Cassini mission are as follows.
1) Rings:
a) Determine scattering properties of rings.
b) Determine ring global properties.
c) Determine additional thermal and compositional properties of rings.
d) Extended ring global properties: low-elevation measurements.
e) Radial scans through optically thin rings (E, F and G).
f) Identify thermal component.
2) Catalog of each satellite's base radar/radiometric properties and their
degree of global variation.
Radio and Plasma Wave Science (RPWS): The RPWS instrument was designed to
study plasma waves, radio emissions, and dust in the Saturn system.
Specific science and measurement objectives were:
1) Aurora and SKR: Obtain radio and plasma wave data which provide
information on the SKR source and plasma waves on auroral field lines.
2) Satellite and ring interactions: Measure dust flux, look for effects of
selective absorption of electrons and ions near rings (thermal
anisotropy), multi-ion wave particle interactions, satellite torii.
3) Inner Magnetosphere: Wave particle interactions via ULF waves; Stability
of trapped electrons and relation to whistler-mode emissions;
ECH (N+ 1/2)fce waves trapped near the equatorial region and heating of
cool electrons.
4) Titan Interactions: Multi-ion species wave-particle interactions;
Evidence of Titan plumes/detached plasma blobs.
5) Magnetospheric Boundaries: Nature of the Saturnian Bow shock: Look for
the signatures of waves accelerating electrons.
6) What is the nature of Saturn's magnetotail? Are there substorms or
other dynamical processes there?
7) Observe lightning via SED and whistlers from Saturn's atmosphere and
possible Titan's.
8) Determine the equatorial dust flux and scale height as a function of
radial distance.
9) Provides for mapping and synoptic measurements required for the RPWS
portion of the magnetospheric survey.
10) Search for electromagnetic phenomena which may be triggers of ring
spokes.
Radio Science Subsystem (RSS): The RSS was designed to study atmospheres
and ionospheres of Saturn, Titan, rings, and gravity fields of Saturn and
its satellites (also, search for gravitational waves during cruise).
Specific science and measurement objectives were:
1) Ring Occultations:
a) To profile radial ring structure with resolution <= 100m;
characterize structure variability with azimuth, wavelength,
ring-opening-angle, and time.
b) To determine the physical particle properties (size distribution,
bulk density, surface density, thickness, viscosity).
c) To study ring kinematics and dynamics (morphology, interaction with
embedded and exterior satellites), and to investigate ring origin
and evolution.
2) Atmospheric Occultations:
a) To determine the global fields of temperature, pressure, and zonal
winds in the stratosphere and troposphere of Saturn.
b) To determine the small scale structure due to eddies and waves.
c) To determine the latitudinal variations of NH3 abundance in
Saturn's atmosphere.
d) To improve the knowledge of H2/He ratio in Saturn's troposphere
(RSS+CIRS).
3) Ionospheric Occultations:
a) To determine the vertical profiles of the electron density in
Saturn's terminator ionosphere, and its variability with latitude.
b) To investigate interaction of the ionosphere with Saturn's
magnetosphere and Saturn's rings.
4) Gravity Field of Saturn:
a) To determine the mass of Saturn and zonal harmonic coefficients of
its gravity field to at least degree 6 (J2, J4, J6).
b) To constrain models of Saturn's interior based on the results
5) Gravity Field and Occultation of Untargeted Satellites:
a) To determine the masses of Mimas, Tethys, Dione, Hyperion, and
Phoebe.
b) To search for a possible tenuous ionosphere around any occulted
satellites (a la Europa and Callisto).
Ultraviolet Imaging Spectrograph (UVIS): The UVIS instrument was designed
to produce spatial UV maps, map ring radial structure, and to determine
hydrogen/deuterium ratios. Specific science and measurement objectives
were:
1) Saturn System Scans:
a) EUV and FUV low resolution spectra of magnetosphere neutral and ion
emissions.
b) System scans at every apoapsis.
2) Satellites:
a) Latitude, longitude and phase coverage coordinated through SSWG.
b) Distant stellar occultations to determine satellite orbits and
Saturn reference frame.
3) Atmosphere:
a) Vertical profiles of H, H2, hydrocarbons, temp in exo,
thermosphere.
b) Long integrations map of hydrocarbons, airglow.
c) Map emissions with highest resolution at the limb.
d) Auroral Map: H and H2 emissions over several rotations.
4) Ring Stellar Occultation Objectives:
a) Highest Radial resolution (20m) structure of rings
b) Discovery and precise characterization of dynamical features
generated by ring-satellite interactions.
- Density waves and bending waves.
- Edge waves and ring shepherding.
- Embedded moonlets and discovery of new moons from
dynamical response in rings.
c) Discovery and precise characterization of azimuthal structure in
rings.
- Eccentric rings.
- Density waves and edge waves.
- Small-scale self-gravitational clumping in rings.
d) Measure temporal variability in ring structure.
e) Simultaneously measure UV reflectance spectrum of rings.
- Determine microstructure on particle surfaces.
- Compositional information on ring particles.
f) Measure size distribution of large particles through occultation
statistics.
g) Measure dust abundance in diffraction aureole.
h) Simultaneously search for flashes from 0.1 m - 1.0 m meteoroid
impacts.
Visible and Infrared Mapping Spectrometer (VIMS): The VIMS instrument was
designed to produce spectral maps to study the composition and structure of
surfaces, atmospheres, and rings. Specific science and measurement
objectives were:
1) Ring Observation:
a) Determine ring composition and its spatial variations.
b) Determine light scattering behavior of rings as a function of I, e,
and alpha.
c) Constrain sizes and surface textures of ring particles.
d) Establish optical depth profile of rings as a function of
wavelength, incidence angle, and longitude.
e) Characterize variable features such as non-circular ringlets,
F ring, spokes, etc., and their evolution.
f) Ring moon compositions.
2) Icy Satellite Observation:
a) Measure UV and NIR spectra to:
- Identify and map surface materials at the highest spatial
resolution.
- Determine microphysical surface properties.
- Provide data on energy balance.
Instrument Host Overview - DSN
================================
Radio Science investigations utilized instrumentation with
elements both on the spacecraft and at the NASA Deep Space Network
(DSN). Much of this was shared equipment, being used for routine
telecommunications as well as for Radio Science.
The Deep Space Network was a telecommunications facility managed by
the Jet Propulsion Laboratory of the California Institute of
Technology for the U.S. National Aeronautics and Space
Administration.
The primary function of the DSN was to provide two-way communications
between the Earth and spacecraft exploring the solar system. To carry
out this function the DSN was equipped with high-power transmitters,
low-noise amplifiers and receivers, and appropriate monitoring and
control systems.
The DSN consisted of three complexes situated at approximately equally
spaced longitudinal intervals around the globe at Goldstone (near
Barstow, California), Robledo (near Madrid, Spain), and Tidbinbilla
(near Canberra, Australia). Two of the complexes were located in the
northern hemisphere while the third was in the southern hemisphere.
The network comprised four subnets, each of which included one antenna
at each complex. The four subnets were defined according to the
properties of their respective antennas: 70-m diameter, standard 34-m
diameter, high-efficiency 34-m diameter, and 26-m diameter.
These DSN complexes, in conjunction with telecommunications subsystems
onboard planetary spacecraft, constituted the major elements of
instrumentation for radio science investigations.
For more information see [ASMAR&RENZETTI1993]"
END_OBJECT = INSTRUMENT_HOST_INFORMATION
OBJECT = INSTRUMENT_HOST_REFERENCE_INFO
REFERENCE_KEY_ID = "ASMAR&RENZETTI1993"
END_OBJECT = INSTRUMENT_HOST_REFERENCE_INFO
OBJECT = INSTRUMENT_HOST_REFERENCE_INFO
REFERENCE_KEY_ID = "JPLD-5564"
END_OBJECT = INSTRUMENT_HOST_REFERENCE_INFO
END_OBJECT = INSTRUMENT_HOST
END
Basic Properties of Files
Each file contains ASCII data for a single day. In addition, for each data file there may be a companion label file with all header and unit information. Most instruments will contribute data at 1 minute intervals. However, some instruments, such as CAPS, will contribute additional processed data at 5 minute intervals. Files are fixed width, space delimited.
Filename
INST_SENS_YYYYDDD_V.TAB
The naming convention for files in the MKP database includes a 4 character instrument name, a 4 character sensor name followed by the year and day. The final character before the .TAB extensionis a version number which in incremented due to datafile updates.
Time In Files
YYY-DOYT00:00:00.000
Time in the files will be given in SCET UTC in the above format.
Cadence
For all instruments, data will be provided at 1 minute centers (Δt) with each point representing an average of the data over that minute. The data begins in each file with a point at time 00:00:30.000 SCET with the average running from 00:00:00 to 00:01:00. Subsequent points are time stamped at the center of the interval ((n-1/2)Δt) with the final point at 1/2Δt less than 24:00:00. Each point represents an average over the time period (n-1)Δt to nΔt. Each file will therefore contain 1440 lines (or less if data points are missing).
For some instruments, CAPS and MIMI for example, higher level data products such as moments of the distribution function (density, velocity) will be provided. These cannot be provided at the 1 minute cadence due to spacecraft motion and instrument articulation. These instrument may provide file with data at a 5 minute cadence. The first data point will cover the time from 00:00:00 to 00:05:00 and will be time stamped at 00:02:30 which is the center of the interval. This way the time stamp will correspond to a data point in the 1 minute files.
Definitions
| X | unit vector in the direction of the x-axis |
| Y | unit vector in the direction of the y-axis |
| Z | unit vector in the direction of the z-axis |
| K | unit vector in the direction of the rotation axis |
| M | unit vector in the direction of the magnetic dipole |
| S | unit vector pointing from Saturn to the Sun |
| V | unit vector pointing along Saturn's orbital motion |
| G | unit vector pointing along the Saturn Prime Meridian as defined in the SPICE/NAIF kernel/td> |
| R | unit vector pointing from the Sun to the spacecraft |
| W | unit vector pointing in the direction of the Sun's rotation axis |
KSM - Kronocentric Solar Magnetospheric
This coordinate system will be similar to the GSM (Geocentric Solar Magnetospheric) coordinate system used at Earth. Because Saturn's rotation axis and magnetic dipole axis are < 1 degree different, we will do not differentiate them when defining this coordinate system. For the Earth, this system would be based on the magnetic dipole axis. Here we will define the system in terms of the rotation axis instead, with the understanding that this is nearly the same as defining it in terms of the dipole axis. The formal definition follows.| X = S | Points from Saturn to the Sun | Y = K x X | Perpendicular to the rotation axis towards dusk | Z = X x Y | Chosen so that the rotation axis lies in the X-Z plane |
KSO - Kronocentric Solar Orbital
This coordinate system will be similar to the GSE (Geocentric Solar Ecliptic) coordinate system used at Earth. At the Earth the y-axis is chosen to lie in the ecliptic plane (the Earth's orbital plane). At Saturn, we will use Saturn's orbital plane as the natural plane by which to define this vector. Note that in this system neither the dipole axis nor the rotation axis necessarily lie along a cardinal direction or in a special plane.| X = S | Points from Saturn to the Sun | Y = -V | Lies in Saturn's orbital plane pointing in the direction opposite Saturn's motion (towards dusk) | Z = X x Y | Perpendicular to the plane of Saturn's motion in the Northward sense |
KG - Kronographic
This coordinate system is equivalent to the IAU-Saturn coordinate system that is defined in the SPICE/NAIF kernels and by the IAU. The Cassini mission has adopted this as a standard. This system is analogous to the geographic (longitude and latitude) system used at the Earth. The KG system is therefore a system that rotates with Saturn. Because the rotation rate of Saturn has some uncertainty, the accuracy of this system in locating features over long time periods is somewhat in question. For this reason it should be used with care. However, the system is well defined by the IAU. This coordinate system should always be used with respect to the official epoch and rotation rate (as defined by the IAU and the project).| X = G | Points along the Saturn Prime Meridian as defined by the IAU | Y = K x X | Lies in the rotational equatorial plane | Z = K | Lies along the rotation axis |
SC - Spacecraft
This coordinate system is fixed relative to the Cassini spacecraft. It is therefore in constant motion as Cassini adjusts its pointing. The coordinate system is useful when comparing measurements between different instruments, especially when studying the pitch angle distributions of particles (relative to the local magnetic field vector). This should not be used for spacecraft trajectory, only for referencing vector field directions.| X | -X is along the MIMI CHEMS, INMS and RPWS Langmuir Field Of View (FOV) | Y | -Y is along the FOV of the ORS instruments | Z | -Z points in the look direction of the High Gain Antenna |
IAU Titan
This is a Titan centered coordinate system as defined by the IAU.RTN - Radial, Tangential, Normal
This coordinate system is based on the location of the spacecraft relative to the Sun and the Sun's rotation axis. It is a spacecraft centered coordinate system. It is most useful for periods when the spacecraft is in interplanetary space.| R = R | Points from the Sun to the spacecraft | T = W x R | The Sun's rotation vector crossed into R | V = X x Y | Completes the right-handed triad |