The spacecraft's structure is built around a rectangular
equipment deck that supports engineering components
and the science instruments. The medium-gain antenna
is on the underside, and the low-gain antennas are mounted
on the solar wings. All the equipment is mounted directly
onto the equipment deck except for the canister, the
concentrator and the collector arrays, which are mounted
inside the sample return capsule, which in turn is mounted
on the equipment deck.
The structures subsystem weighs
98.6 kilograms (217.4 pounds).
Spacecraft Configuration Diagrams
The sample return capsule is a blunt-nosed cone with
a diameter of 152 centimeters (60 inches). It has five
major components: a heat shield, backshell, sample return
canister, parachute system and avionics.
The total mass of the capsule, including the parachute
system, is 205 kilograms (420 pounds).
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 mechanism to extend the collector arrays. The
capsule is encased in a carbon impregnated material
known as carbon-carbon and an ablative material called
SLA- 561 to protect the samples stowed in its interior
from the heat of reentry. A parachute activated 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 outermost
thermal protection layer is made of carbon-carbon. The
capsule heat shield remains attached to the capsule
throughout descent and serves as a protective cover
for the sample canister at touchdown. The heat shield
is designed to remove 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
cork-based material called SLA-561V that was developed
by Lockheed Martin for use on the Viking missions to Mars,
and have been used on several missions including Genesis,
Pathfinder, Stardust and the Mars Exploration Rover missions.
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 science canister is an aluminum enclosure containing
the specialized collector arrays and ion concentrator.
On the inside of the lid of the science canister is
a bulk solar wind collector array. The specialized collector
arrays are rotated out from inside the science canister.
Underneath the stowed collector arrays, the ion concentrator
forms the bottom of the science canister. The canister
is inside the sample return capsule, which is mounted
to an equipment deck suspended between the backshell
and heat shield on a set of support struts.
The parachute system consists of a mortar-deployed
2.1-meter (6.8-foot) drogue chute to provide stability
at supersonic speeds, and a main chute 10.5 by 3.1 meters
(about 34.6 by 12.1 feet).
Inside the 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
33 kilometers (108,000 feet) 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 6.7 kilometers
altitude (22,000 feet). As the drogue chute moves away,
it will extract the main chute. At the time of capture,
the capsule will be traveling forward at approximately
12 meters per second (30 miles per hour) and descending
at approximately 4 meters per second (9 miles per hour).
The solar arrays were stowed during launch and then released.
Mechanisms under the wings allowed them to unfold and
move on a hinge until two latches per wing engaged and
locked the wings in place.
The sample return capsule has a separation and release
system, made of three two legged struts that hold the
sample return capsule in place. The sample return capsule
is mounted on its struts with its heat shield atop six
spring-loaded cans. The springs push on a ring that
presses against the heat shield and gently shoves the
capsule away from the spacecraft when pyrotechnic bolts
The sample return capsule's lid opens and closes on
a main hinge, and all the electronic signals that control
the collector arrays and concentrator are passed through
a wire harness from the spacecraft to the capsule that
passes through the hinge. 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 ion and electron monitors each had
a door mechanism that exposed the sensors inside by
using pyrotechnics to expand small metallic balloons
to open the door.
Four mechanical latch/hook assemblies worked to grab
the lid of the sample return capsule and hold it in
place throughout launch. The science canister mechanisms
are: the lock ring device, sealing lid, canister lid
mechanisms, and solar collector array deployment mechanism.
All of the canister mechanisms combined weigh 17.0
kilograms (37.5 pounds)
Genesis receives its commands and sequences from Earth
and translates them into spacecraft actions. The flight
software is capable of running multiple concurrent sequences,
as well as executing immediate commands as they are received.
The software used during the collection mission interpreted
data from the ion and electron monitors to deploy the
proper collectors depending on the type of solar wind.
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 for the ground to
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. A software fault protection
system is used to protect the spacecraft from reasonable,
credible faults but also has resiliency built into it
so any faults not anticipated can be accommodated without
placing the spacecraft in a safe state.
All of the spacecraft's computing functions are performed
by the command and data handling subsystem. The heart
of this subsystem is a RAD6000 computer, a radiation
hardened version of the PowerPC chip used on some personal
computers and videogame systems. 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 are used to communicate with external
peripherals. They allow the use of redundant, identical
sets of 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 entire command and data handling subsystem weighs
11.9 kilograms (26.2 pounds).
Genesis' telecommunications subsystem is composed of both
a radio system operating in the S-band microwave frequency
range and a system that operates in the ultra high frequency
(UHF) range. The S-band system provides communication
capability between Earth and the spacecraft throughout
all phases of the mission. The UHF system is located in
the sample return capsule; after parafoil deployment,
it provides a backup tracking capability.
The spacecraft's radio system communicates with Earth
though a medium-gain antenna. The medium-gain 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
houses four low-gain antennas, located on the underside
of the craft. These are patch antennas, which sit on
a coaster-size square (10 by 10 by 1 centimeters (4
by 4 by 0.4 inches)). These have a much wider field
The low-gain antennas will be used to make initial
contact with the spacecraft after it leaves Earth's
atmosphere, and afterwards only 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
All of the spacecraft's power is generated, stored and
distributed by the electrical power subsystem. The system
obtains its power from an array of standard silicon
solar cells arranged on two panels on either side of
the equipment deck. The two solar panel wings, made
of silicon and aluminum, are fixed in place. They hold
grids of silicon cells which generate 265 watts at Earth's
distance from the Sun. A power distribution and drive
unit contains switches that send power to various loads
around the spacecraft. Power is also stored in a 16-amp-hour
nickel hydrogen battery.
The electrical system also contains a pyro initiator
unit which fires small explosive devices that configure
the spacecraft following launch, performing such tasks
as extending Genesis' solar array and opening covers
on science instruments. The pyrotechnic system also
releases the sample return capsule by actuating cable
cutters to allow the heat shield and back shell to separate
from the spacecraft's body.
The electrical power subsystem weighs 36.5 kilograms
Genesis maintains its orientation in space, or "attitude,"
by continuously spinning in space. The attitude control
system will keep Genesis spinning at a rate of 1.6 revolutions
per minute. During the science mission, the axis of spin
pointed 4 degrees ahead of the Sun, so that ion and electron
monitors would face directly into the oncoming solar wind.
The slow spin helps maintain inertial pointing at the
Sun, and minimizes pointing errors due to solar radiation
pressure torques. Genesis determines its orientation at
any given time using a star tracker and Sun sensors.
Genesis is the first robotic spacecraft to fly this
particular system to determine its orientation, or "attitude."
The star tracker can track stars of third magnitude
or fainter; in combination with the digital Sun sensor,
it can identify stars and generate information on the
spacecraft's attitude. Using both the angles of the
Sun and of nearby stars, on-board software can determine
the spacecraft's orientation and spin rate. As long
as the spacecraft is spinning between 1.6 and 2 revolutions
per minute, it can identify stars. During the maneuvers
when the spacecraft is spinning faster than 2 rpm, the
spacecraft will use its spinning Sun sensors to determine
its orientation. There are two star trackers, two digital
sun sensor and two spinning sun sensors onboard as redundant
The guidance, navigation and control subsystem weighs
10.0 kilograms (22.0 pounds).
The propulsion subsystem features sets of two kinds of
small thrusters. The larger are used to make major trajectory
correction maneuvers, and the smaller to continually maintain
the spacecraft in its orbit.
Firing the thrusters changes the spacecraft's orientation.
Two clusters of four small hydrazine thrusters each are
mounted on the spacecraft, providing 0.88 newtons (0.2
pounds) of thrust each for small maneuvers to keep the
spacecraft in orbit and to increase or reduce the rotation
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 in
order to avoid contaminating the solar samples.
In addition to miscellaneous tubing, latch valves and
filters, the propulsion subsystem also includes two 55-centimeter-diameter
(22-inch) fuel tanks, each containing hydrazine, pressurized
with gaseous helium. The outlets of tanks are metered
together and will draw together equally.
The propulsion subsystem weighs 36.6 kilograms (80.7 pounds).
The thermal control subsystem is responsible for maintaining
the temperatures of each component on the spacecraft to
within their allowable limits. It does this using a combination
of active and passive control elements. The active components
are the heaters. The passive components are thermal paint,
blankets of black kapton on the backside of the spacecraft
and blankets of indium-10 oxide on the sunward side.
The thermal control subsystem weighs 15.9 kilograms
Genesis is sponsored by NASA's Discovery Program, which
competitively selects lowcost solar system exploration
missions with highly focused science goals. The Jet Propulsion
Laboratory, Pasadena, Calif., manages the Genesis mission
for NASA's Office of Space Science, Washington, D.C. Lockheed
Martin Astronautics, Denver, Colo., designed and built
the spacecraft and will operate it jointly with JPL. JPL
is a division of the California Institute of Technology,
the home institute of the principal investigator. Major
portions of the payload design and fabrication were carried
out at Los Alamos National Laboratory.
Learn more about Spacecraft Partners
Curator: Aimee Meyer
Updated: November 2009