INSTRUMENT_HOST_DESC |
Instrument Host Overview
========================
For most Phoenix Mars Scout Lander experiments, data was collected by
instruments on the spacecraft. Those data were then relayed directly
to stations of the NASA Deep Space Network (DSN) on Earth or
indirectly using the Mars orbiters Mars Global Surveyor (MGS) or 2001
Mars Odyssey (ODY). The following sections provide an overview first
of the Phoenix spacecraft, then of the DSN ground system, and finally
of the 2001 Mars Odyssey, as each supported Phoenix science
activities.
Instrument Host Description
===========================
The Mars Phoenix Lander was build for the canceled Mars 2000 Lander
Mission. The spacecraft was refurbished and held as the instrument
host for the Phoenix mission [SMITHETAL2008]. Phoenix was the first
of the Scout class mission and consisted of a single lander with
associated instrumentation. The Lander was about 18 feet (5.5 meters)
long with the solar panels deployed, and the science deck by itself
was about 5 feet (1.5 meters) in diameter. From the ground to the top
of the MET mast, the Lander measured about 7 feet (2.2 meters) tall.
The Lander weighed 350 kg, or 770 lbs. It was launched on August 4,
2007, on a Delta II 7925 launch vehicle, and was operational until
November 2, 2008, performing on the Martian surface for 152 sols.
Power was generated during the cruise stage by two gallium arsenide
solar panels (total area 3.1 m2, or 33 ft2) mounted to the cruise
stage. After touchdown, Phoenix relied on two octagonal gallium
arsenide solar panel wings extending from the Lander base to charge
its battery for operations. Input from the solar panels was
sufficient to power daytime operations, but nighttime operations
required additional power from the Lander heater system.
Phoenix communicated directly with Earth using the X-band portion of
the radio spectrum (8 to 12 gigahertz) throughout the launch and
cruise stages. Continuous and instantaneous communication with the
spacecraft was maintained throughout the launch phase, switching to
communication every three days in the cruise phase. All X-band
capability was lost once the cruise stage was jettisoned. During the
surface mission, the landed Helix antenna on the Lander deck
communicated with DSN via the orbiters Mars Express (MRO), Mars
Odyssey (ODY), and Mars Express (MEX) every four to eight hours.
Other Lander systems included a single RAD6000 processor, a fault
detection and correction system for monitoring spacecraft health, a
guidance system to land the spacecraft, a propulsion system for
touchdown, a data handling system for committing critical data to
overnight storage during surface operations, and a heater system to
ensure the spacecraft maintained an appropriate temperature . The
Lander served as a host for various associated instrumentation,
including six instrument packages: the Surface Stereo Imager (SSI),
Robotic Arm (RA) and associated Icy Soil Acquisition Device (ISAD),
the Robotic Arm Camera (RAC), the Microscopy, Electrochemistry, and
Conductivity Analyzer (MECA), the Thermal Evolved Gas Analyzer (TEGA),
and the Meteorological Package (MET) [SMITHETAL2008].
During most of Entry, Descent, and Landing (EDL), Phoenix used a UHF
antenna that wrapped around the backshell to give it a wide field of
view (FOV) for communications. During terminal descent (approximately
30 seconds before landing), the Lander switched to the landed Helix
antenna and continued transmitting a UHF signal until one minute
after landing. This wide FOV was necessary as the geometry between
Phoenix and the orbiters MRO, ODY, and MEX required a very wide
spread of off-boresight angles.
Following its soft touchdown between 65 deg N to 72 deg N latitude,
and after waiting 20 minutes for the dust to settle, the Lander
performed a number of critical activities. These 'Sol 0' (a sol is a
mars day) activities included deployments of the landed solar arrays,
the bio-barrier covering the RA, and the SSI and MET masts. The SSI
took images of the bio-barrier, solar arrays, and part of the footpad
and workspace. High priority EDL and Sol 0 data were saved to flash
memory within the first hour after touchdown, after which the Lander
went to sleep to conserve energy. The Lander woke up for 10 minutes
for the first post-landed UHF communication pass one ODY or MRO orbit
period (approximately 2 hours) after landing. After relaying data to
the orbiters during that first pass, the Lander went to sleep again.
Payload heaters were on continuously from touchdown, with Lander
heaters kicking in around midnight for 4-5 hours of keep-alive
heating. [GUINNETAL2008]
Lander on the Surface of Mars
=============================
The first seven sols after Landing were known as the characterization
phase, with pre-planned activities running from a minimum of 3 hours
on Sol 1 to a maximum of 6.5 hours on Sol 6 (the Lander was active
for up to 7 hours during the nominal surface or digging phase). The
performance of the spacecraft's power, thermal, and UHF subsystems
were thoroughly characterized during this phase, and TEGA, MECA, and
MET instruments went through their initial checkouts and prepared for
nominal operations. Concurrent with these activities, the EDL and Sol
0 data that were stored in the non-volatile (flash memory) were
relayed to the ground. The SSI imaged as much of the Lander as it
could see and characterized the workspace and surrounding
environment. The RAC located on the 'wrist' of the RA was used to
image the footpads and the TEGA cover, as it was the only imager that
could be maneuvered into the proper viewpoint for these pictures.
After the Robotic Arm (RA) was checked out, the digging phase
commenced. The digging phase activities included digging a trench in
front of the Lander, and the analysis of soil samples at various
trench-depths by the Lander instruments. This phase continued until
the End-of-Mission on Sol 90. Operations during this phase were
conducted at the University of Arizona.
The Lander operated for 152 sols and achieved all scientific
objectives.
Instrument Host Overview - DSN
==============================
The Deep Space Network is a telecommunications facility managed
by the Jet Propulsion Laboratory of the California Institute of
Technology for the U.S. National Aeronautics and Space
Administration (NASA).
The primary function of the DSN is to provide two-way
communications between the Earth and spacecraft exploring the
solar system. To carry out this function it is equipped with
high-power transmitters, low-noise amplifiers and receivers,
and appropriate monitoring and control systems.
The DSN consists 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 are located in the northern hemisphere while the
third is in the southern hemisphere.
Each complex includes several antennas, defined by their
diameters, construction, or operational characteristics:
70-m diameter, standard 34-m diameter, high-efficiency 34-m
diameter (HEF), and 34-m beam waveguide (BWG).
For more information see [ASMAR&RENZETTI1993].
Instrument Host Overview - 2001 Mars Odyssey
============================================
The 2001 Mars Odyssey (ODY) spacecraft was built by Lockheed Martin
Astronautics (LMA). Most spacecraft systems were redundant
in order to provide backup should a device fail. In addition
to transmitting data collected by ODY instruments and systems,
the telecommunications system was used to relay data from Mars
surface assets and measure their relative motion radiometrically
in the 400 MHz frequency range. For more information, see
[JPLD-16303].
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