The Genesis spacecraft
NASA FACT SHEET
Posted: July 28, 2001
The Genesis spacecraft incorporates innovative, state-of-the-art technologies pioneered by other recent missions, and uses off-the-shelf spacecraft components, designs and, in some cases, spare parts and instrumentation left over from previous missions.
There are five major science elements in the Genesis payload: the science canister, a stack of collector arrays, the ion concentrator, the electron monitor and the ion monitor. The science canister includes a bulk collector array mounted on its lid, and also houses the collector array stack and the ion concentrator.
Sample Return Capsule
A hinged clamshell mechanism opens and closes the capsule. The science canister -- housing the solar wind collector arrays and ion concentrator -- fits inside, with a central rotating shaft to extend the collector arrays into the solar wind. The capsule is encased in carbon-carbon heat shielding and a silicone-based ablative material called SLA-561 to protect the samples stowed in its interior from the heat of reentry. A parachute deployed by a mortar unit is carried inside the capsule and will be used to slow its descent.
The heat shield is made of a graphite-epoxy composite covered with a thermal protection system. The thermal protection system is made of a carbon-impregnated material manufactured by Lockheed Martin Astronautics, Denver, Colo., called carbon-carbon. The capsule heat shield will remain attached to the capsule throughout descent and serve as a protective cover for the sample canister at touchdown. The aeroshell is designed to dissipate into the atmosphere more than 99 percent of the initial kinetic energy of the sample return capsule.
The backshell structure is also made of a graphite-epoxy composite covered with a thermal protection system: a silicone-based material called SLA-561V that was developed by Lockheed Martin for use on the Viking missions to Mars and that is currently used on the Space Shuttle external tank. The backshell provides the attachment points for the parachute system, and protects the capsule from the effects of recirculation flow of heat around the capsule.
The parachute system consists of a mortar-deployed 1.6-meter (5.25-foot) drogue chute to provide stability at supersonic speeds, and a main chute 10 by 4 meters (about 33 by 13 feet) that is released at an altitude of about 6 kilometers (approximately 20,000 feet). The system incorporates the two parachutes into a single parachute canister.
Inside the parachute canister, a gas cartridge will pressurize a mortar tube and expel the drogue chute. The drogue chute will be deployed at an altitude of approximately 30 kilometers (about 20 miles) above mean sea level to provide stability to the capsule until the main chute is released. A gravity-switch sensor and timer will initiate release of the drogue chute. Based on information from timer and backup pressure transducers, a small pyrotechnic device will cut the drogue chute from the capsule at about 20 kilometers altitude (12 miles). As the drogue chute moves away, it will extract the main chute from the parachute canister. At the time of capture, the capsule will be traveling at about 5 meters per second (roughly 10 miles per hour).
Command and Data Handling
With 128 megabytes of random access memory and three megabytes of non-volatile memory, which allows the system to maintain data even without power, the subsystem runs Genesis' flight software and controls the spacecraft through interface electronics. 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. 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 Genesis' sensors that measure the spacecraft's 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 Genesis' telecommunications subsystems is done 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 provides the spacecraft time. A converter card takes power from the electrical power subsystem and converts it into the proper voltages for the rest of the command and data handling subsystem components.
The command and data handling subsystem weighs 11.9 kilograms (26.2 pounds).
The spacecraft's radio system communicates with Earth primarily through a medium-gain antenna. This antenna is spiral-shaped, about 10 centimeters (4 inches) in diameter, about 12 centimeters (4.87 inches) tall and weighs 105 grams (about 4 ounces).
The spacecraft also uses four low-gain antennas, located on the solar arrays. These are patch antennas, which sit on a coaster-sized square (10 by 10 by 1 centimeters (4 by 4 by 0.4 inches)). These have a much wider field of view.
The low-gain antennas will be used to make initial contact with the spacecraft after it leaves the Delta rocket's third stage, and afterwards only near Earth during the return or for emergencies. The medium-gain antenna will be used for most of the spacecraft's communication with Earth.
The telecommunication subsystem weighs 10.1 kilograms (22.3 pounds).
The electrical system also contains a pyro initiator unit which fires small explosive devices that configure the spacecraft following launch, performing such tasks as unlatching Genesis' solar arrays when they are deployed and opening covers on the electron and ion monitors. The pyrotechnic system also releases the sample return capsule.
The electrical power subsystem weighs 36.5 kilograms (80.5 pounds).
Guidance, Navigation and Control
Genesis determines its orientation at any given time using a star tracker in combination with Sun sensors. The star tracker can track stars of third magnitude or brighter; Genesis then processes star tracker data in its main onboard computer to recognize any star patterns as they pass through the tracker's field of view. The spacecraft uses both the directions of the Sun and of stars as measured by the Sun sensors and star tracker, respectively, to determine its orientation in space. As long as the spacecraft is spinning below about 2 rpm, it can use stars and thus determine its orientation more accurately. During maneuvers when the spacecraft is spinning faster than 2 rpm, the spacecraft will use its Sun sensors to determine a sufficiently accurate orientation. There are two star trackers on board to back each other up, and the Sun sensors also back each other up.
The guidance, navigation and control subsystem weighs 10.0 kilograms (22.0 pounds).
Firing the thrusters changes the spacecraft's orientation. Two clusters of four small hydrazine thrusters each are mounted to the aft side (away from the Sun) of the spacecraft's deck, providing 0.88 newtons (0.2 pounds) of thrust each for small maneuvers to keep the spacecraft in its desired orientation and orbit, and to increase or reduce the spacecraft's spin rate. Four more thrusters are also mounted on the spacecraft, each providing 22.2 newtons (5 pounds of thrust) for major trajectory correction maneuvers. These thrusters are only used when the sample return capsule's lid is closed, so that the exhaust does not contaminate the solar samples.
In addition to miscellaneous tubing, pyro valves and filters, the propulsion subsystem also includes two 55-centimeter-diameter (22-inch) propellant tanks, each containing hydrazine, pressurized with gaseous helium.
The propulsion subsystem weighs 36.6 kilograms (80.7 pounds).
The structures subsystem weighs 98.6 kilograms (217.4 pounds).
The passive components are black and white thermal paint as well as multilayer insulation blankets, some with an outer layer of carbon-impregnated black kapton, and some with an outer layer of indium-tin-oxide-coated kapton that has a gold color due to an aluminum backing that reflects light through the transparent yellow kapton.
The thermal control subsystem weighs 15.9 kilograms (35.1 pounds).
The sample return capsule has three two-legged struts that hold it in place. The sample return capsule is mounted on its struts with its nose atop six spring-loaded cans. Following release of the struts, a ring between these cans and the nose gently shoves the capsule off its platform.
The sample return capsule's lid opens and closes on a main hinge, which is tethered to the deck. In order to keep the hinge from damaging the sample return capsule as it plunges through Earth's atmosphere, the hinge is retracted away from the capsule before reentry. Elbow joints at the top of the hinge have separation bolts and cable cutters that separate and retract the hinge assembly. The hinge carries with it the severed cables that allowed communication between the capsule and the rest of the spacecraft.
The ion and electron monitors each have a door mechanism that exposes their sensors by using pyrotechnics to expand small metallic balloons to open the doors.
Four mechanical latch/hook assemblies work to grab the lid of the sample return capsule and hold it in place throughout launch and reentry. The science canister mechanisms are: the lock ring device, canister lid mechanism and collector array deployment mechanism.
All of the mechanisms combined weigh 17.0 kilograms (37.5 pounds).
The software used during the data collection will determine solar wind conditions based on data from the ion and electron monitors. It will then command collection arrays to an appropriate configuration and adjust the ion concentrator's voltage.
The flight software is also responsible for a number of autonomous functions, such as attitude control and fault protection, which involve frequent internal checks to determine whether a problem has occurred. If the software senses a problem, it will automatically perform a number of preset actions to resolve the problem or put the spacecraft in a safe mode until the ground can respond.
A software fault protection system is used to protect the spacecraft from reasonable, credible faults but also has resiliency built into it so that many faults not anticipated can be accommodated without placing the spacecraft in a safe state.
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Flight Data File
Vehicle: Delta 2 (7326)
Launch date: Aug. 1, 2001
Launch time: 12:31:38 p.m. EDT (1631:38 GMT)
Launch site: SLC-17A, Cape Canaveral, Florida
Satellite broadcast: GE-2, Trans. 9, C-band
Launch timeline - Chart with times and descriptions of events to occur during the launch.
Ground track - Trace the Delta rocket's trek during launch.
Launch windows - See the daily launch opportunities for Genesis.
Delta 2 rocket - Overview of the Delta 2 7326-model rocket used to launch Genesis.
Mission science - Overview of the scientific objectives of Genesis.
Delta directory - See our coverage of preview Delta rocket flights.
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