The 2001 Mars Odyssey spacecraft
NASA FACT SHEET
Posted: April 5, 2001
The framework of the spacecraft is composed mostly of aluminum and some titanium. The use of titanium, a lighter and more expensive metal, is an efficient way of conserving mass while retaining strength. Odyssey's metal structure is similar to that used in the construction of high-performance and fighter aircraft.
Most systems on the spacecraft are fully redundant. This means that, in the event of a device failure, there is a backup system to compensate. The main exception is a memory card that collects imaging data from the thermal emission imaging system.
Command and Data Handling
Interface electronics make use of computer cards to communicate with external peripherals. These cards slip into slots in the computer's main board, giving the system specific functions it would not have otherwise. For redundancy purposes, there are two identical strings of these computer and interface electronics, so that if one fails the spacecraft can switch to the other.
Communication with Odyssey's sensors that measure the spacecraft' orientation in space, or "attitude," and its science instruments is done via another interface card. A master input/output card collects signals from around the spacecraft and also sends commands to the electrical power subsystem. The interface to Odyssey's telecommunications subsystems exists through another card called the uplink/downlink card.
There are two other boards in the command and data handling subsystem, both internally redundant. The module interface card controls when the spacecraft switches to backup hardware and serves as the spacecraft's time clock. A converter card takes electricity produced by the power subsystem and converts it into the proper voltages for the rest of the command and data handling subsystem components. The last interface card is a single, non-redundant, one-gigabyte mass memory card that is used to store imaging data. The entire command and data handling subsystem weighs 11.1 kilograms (24.5 pounds).
The electrical power subsystem operates the gimbal drives on the high-gain antenna and the solar array. It contains also a pyro initiator unit, which fires pyrotechnically actuated valves, activates burn wires, and opens and closes thruster valves. The electrical power subsystem weighs 86.0 kilograms (189.6 pounds).
Guidance, Navigation and Control
This system also includes the reaction wheels, gyro-like devices used along with thrusters to control the spacecraft's orientation. Like most spacecraft, Odyssey's orientation is held fixed in relation to space ("three-axis stabilized") as opposed to being sta-bilized via spinning. There are a total of four reaction wheels, with three used for primary control and one as a backup. The guidance, navigation and control subsystem weighs 23.4 kilograms (51.6 pounds).
The main engine, which uses hydrazine propellant with nitrogen tetroxide as an oxidizer, produces a minimum thrust of 65.3 kilograms of force (144 pounds of force). Each of the four thrusters used for attitude control produce a thrust of 0.1 kilogram of force (0.2 pound of force). Four 2.3-kilogram-force (5.0-pound-force) thrusters are used for turning the spacecraft.
In addition to miscellaneous tubing, pyro valves and filters, the propulsion subsystem also includes a single gaseous helium tank used to pressurize the fuel and oxidizer tanks. The propulsion subsystem weighs 49.7 kilograms (109.6 pounds).
There are also four retention and release devices used for the solar array. The three panels of the array are folded together and locked down for launch. After deployment, the solar array is also controlled using a two-axis gimbal assembly.
The last mechanism is a retention and release device for the deployable 6-meter (19.7-feet) boom for the gamma ray spectrometer. All of the mechanisms combined weigh 24.2 kilograms (53.4 pounds).
The software responsible for the data collection is extremely flexible. It collects data from the science and engineering devices and puts them in a variety of holding bins. The choice of which channel is routed to which holding bin, and how often it is sampled, is easily modified via ground commands.
The flight software is also responsible for a number of autonomous functions, such as attitude control and fault protection, which involves frequent internal checks to determine if a problem has occurred. If the software senses a problem, it will automatically perform a number of preset actions to resolve the problem and put the spacecraft in a safe standby awaiting further direction from ground controllers.
Flight Data File
Vehicle: Delta 2 (7925)
Payload: 2001 Mars Odyssey
Launch date: April 7, 2001
Launch times: 11:02 a.m. EDT or 11:32 a.m. EDT
Launch site: SLC-17A, Cape Canaveral, Fla.
Launch windows - See the daily launch times available for Mars Odyssey to lift off over the 20-day planetary alignment.
Launch timeline No. 1 - Chart with times and descriptions of events to occur during the launch first daily opportunity is used.
Launch timeline No. 2 - Chart with times and descriptions of events to occur during the launch second daily opportunity is used.
Ground track - Trace the Delta rocket's trek during launch.
Restricted zone - Map outlining the Launch Hazard Area where mariners should remain clear for the liftoff.
Delta 2 rocket - Overview of the Delta 2 7925-model rocket used to launch Mars Odyssey.
Mission science - Overview of the scientific objectives of Mars Odyssey.
Delta directory - See our coverage of preview Delta rocket flights.
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