Phoenix 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].