Space 
A Planetary Probe Specs and Science InstrumentsLike a example of a planetary probe specs and science instruments let's get acquainted with the Stardust spacecraft. The Stardust spacecraft was support to a NASA's mission which had launched by early 1999 and had successfully passed close to comet Wild 2 in January 2004, collecting cometary dust as it eventually came by Earth to release a sample-ladden capsule in January 2006. NASA then, since the summer of 2007 had extended the craft mission under the name Stardust-NExT, to a second flyby of comet Tempel 1, by Feb. 14, 2011, while is was to be returning from a close approach to the Sun and as the comet had been the object of the Deep Impact mission in 2005 which had had a load impacting at the surface. The craft successfully flew over Tempel 1 in February 2011
 | A View of the Stardust Spacecraft. picture courtesy site 'Amateur Astronomy' based on a picture NASA/JPL-Caltech/LMSS |
When it launched in 1999, Stardust carried onboard some of the most innovative, state-of-the-art technologies pioneered by other recent missions. It combined this state-of-the-art technology with a combination of off-the-shelf spacecraft components and, in some cases, spare parts and instrumentation left over from previous successful space missions. The Stardust spacecraft is derived from a rectangular deep-space bus called SpaceProbe developed by Lockheed Martin Space Systems, Denver. The main bus is 5.6 ft (1.7 meters) high, 2.16 ft (0.66 meter) wide and 2.16 ft (0.66 meter) deep, which is about the size of an average office desk. With its two parallel solar panels deployed, the spacecraft takes on the shape of a letter H. As far as the propulsion system is concerned, The Stardust spacecraft was deviced with only a relatively modest propulsion system because of its carefully designed trajectory, which included three loops around the Sun with flybys of Earth, comet Wild 2 and an asteroid, plus its return to Earth after the comet flyby. The spacecraft is equipped with two sets of thrusters that use hydrazine as a monopropellant. Eight larger thrusters, each of which puts out 4.4 newtons (1 pound) of thrust, are used for trajectory correction maneuvers as eight smaller thrusters producing 0.9 newton (0.2 pound) of thrust each are used to control the spacecraft’s attitude, or orientation. The thrusters are in four clusters. At launch, the spacecraft carried 187 pounds (85 kilograms) of hydrazine propellant
The attitude control system manages the spacecraft’s orientation in space. Like most solar system exploration spacecraft, Stardust is three-axis stabilized, meaning that its orientation is held fixed in relation to space, as opposed to spacecraft that stabilize themselves by spinning. Stardust determines its orientation at any given time using a star camera or one of two inertial measurement units, each of which consists of three ring-laser gyroscopes and three accelerometers. The spacecraft’s orientation is changed by firing thrusters. The inertial measurement units are needed only during trajectory correction maneuvers and during the fly-through of the cometary coma, when stars may be difficult to detect. Otherwise, the vehicle can be operated in a mode using only stellar guidance for spacecraft positioning. Two Sun sensors serve as backup units, coming into play if needed to augment or replace the information provided by the rest of the attitude control system’s elements
Virtually all spacecraft components are redundant, with critical items “cross-strapped” or interconnected so that they can be switched in or out most efficiently. The battery includes an extra pair of cells. Fault protection software is designed so that the spacecraft is protected from commonly known faults without unnecessarily putting the spacecraft into a safe mode due to unanticipated but probably benign glitches. The Whipple Shields, shields that protect Stardust from the blast of cometary particles is named for American astronomer Dr. Fred L. Whipple, who in 1950 developed the “dirty snowball” model of the cometary nucleus as a mixture of dark organic material, rocky grains and water ice. Whipple also came up with the idea of shielding spacecraft from high-speed collisions with the bits and pieces from comets and asteroids that are ejected as they circle the Sun. The system includes two bumpers at the front of the spacecraft, which protect the solar panels, and another shield protecting the main spacecraft body. Each of the shields is built around composite panels designed to disperse particles as they impact, augmented by blankets of a ceramic cloth that further dissipate and spread particle debris. The Whipple Shield was designed to protect Stardust from impacts of comet fragments as large as about 0.4 inch (1 centimeter)
The spacecraft’s computer is craft's brain and it is embedded in the spacecraft’s command and data-handling subsystem, and provides computing capability for all spacecraft subsystems. At its heart is a RAD6000 processor, a radiation-hardened version of the PowerPC chip used on some models of Macintosh computers. It can be switched between clock speeds of 5, 10 or 20 MHz. The computer includes 128 megabytes of random-access memory (RAM); unlike many previous spacecraft (but common today), Stardust does not have an onboard tape recorder but instead stores data in its RAM for transmission to Earth. The computer also has 3 megabytes of programmable memory that can keep stored data even when the computer is powered off. The spacecraft uses about 20 percent of the 128 megabytes of data storage for its own internal housekeeping. The rest of the memory is used to store science data and for computer programs that control science observations. Memory allocated to specific instruments includes about 75 megabytes for images taken by the navigation camera, 13 megabytes for data from the comet and interstellar dust analyzer, and 2 megabytes for data from the dust flux monitor. Two solar array panels, made of a core of aluminum honeycomb, with outer layers of graphite fibers and polycyanate face sheets, affixed to the spacecraft were deployed shortly after launch. Together they provide 7.9-square yards (6.6-square meters) of solar collecting area using high-efficiency silicon solar cells. One 16-amp-hour nickel-hydrogen battery provides power when the solar arrays are pointed away from the Sun and during peak power operations. Stardust’s thermal control subsystem uses louvers to control the temperature of the inertial measurement units and the telecommunications system’s solid-state power amplifiers. Thermal coatings and multilayer insulation blankets and heaters are used to control the temperature of other parts of the spacecraft
Stardust is equipped with a transponder (radio transmitter/receiver), originally developed for NASA's Cassini mission to Saturn, as well as a 15-watt radio frequency solid-state amplifier. Data rates will range from 40 to 33,000 bits per second. During cruise, communications are mainly conducted through the spacecraft’s medium-gain antenna. Three low-gain antennas are used for initial communications near Earth and to receive commands when the spacecraft is in nearly any orientation. A 2-foot (0.6-meter)-diameter high-gain dish antenna is used primarily for communication following comet encounter. The antenna is fixed to the “top” of the spacecraft body. Stardust will use the high-gain antenna to transmit images of the comet, as well as data from the Comet and Interstellar Dust Analyzer and the Dust Flux Monitor, at a high data rate to minimize the transmission time and the risk of losing data during the extended time that would be required to transmit the data through the medium-gain antenna. Most data from the spacecraft will be received through the Deep Space Network’s 112-foot (34-meter)-diameter ground antennas, but the network's 230-foot (70-meter) antennas will also be used during some critical telecommunications phases, such as when Stardust transmits science data during and after comet encounter
There are three dedicated science packages on Stardust -the two-sided Dust Collector, the Comet and Interstellar Dust Analyzer, and the Dust Flux Monitor. Science data are also being obtained without dedicated hardware. The navigation camera, for example, provides images of its cometary target for both targeting accuracy and scientific analysis
