PDS_VERSION_ID = PDS3 OBJECT = INSTRUMENT_HOST INSTRUMENT_HOST_ID = VG2 OBJECT = INSTRUMENT_HOST_INFORMATION INSTRUMENT_HOST_NAME = "VOYAGER 2" INSTRUMENT_HOST_TYPE = SPACECRAFT INSTRUMENT_HOST_DESC = " Spacecraft Overview =================== Reference is [Morrison, 1982]. The two identical Voyager spacecraft, each with a mass of 815 kilograms, are among the most autonomous, sophisticated robots ever sent to explore other worlds. Each is a self-contained system, carrying its own power, propulsion, communications systems, and science instruments. Communication between the spacecraft and Earth is carried out via a high-gain radio antenna 3.7 meters in diameter that is always oriented toward the Earth. The radio transmitters (there are two complete systems to provide backup in case of failure) have only 23 watts of transmitting power, about the power of a refrigerator light bulb. Yet with the aid of the sensitive receivers of the NASA Deep Space Network of tracking stations, this 23-watt radio can transmit data over a distance of 1 billion kilometers at the enormous rate of 115200 bits per second, almost a hundred times faster than Pioneer. At the greater distance to Saturn, a lower data rate of 44800 bits per second was adopted. In addition, the Voyager spacecraft carried a digital tape recorder with a storage capacity of 500 million bits. The power for each Voyager spacecraft is supplied by three radioisotope thermoelectric generators (RTGs) that produce about 400 watts of electrical power. Each spacecraft is controlled by a set of interconnected electronic brains called the attitude and articulation control subsystem (AACS), the flight data subsystem (FDS) and the computer command subsystem (CCS). Rather than being instructed directly by ground controllers (as were the pioneers), the Voyager control systems accept precoded sets of several thousand instructions that can provide autonomous operation for days or weeks at a time. These systems also include elaborate error detection and correction routines so the spacecraft can locate and correct problems before ground controllers are aware of them. The AACS, FDS, and CCS can be reprogrammed in flight if necessary, allowing great flexibility in responding to changing conditions or science objectives.' Platform Descriptions ===================== Platform MAGNETOMETER BOOM -------------------------- A 13-meter-long boom that was unfurled and extended automatically after launch Platform SCAN PLATFORM ---------------------- The part of the Voyager spacecraft that carries the imaging, IRIS, ultraviolet, and photopolarimeter instruments. It can be pointed to any part of the sky by rotating around two axes (azimuth and elevation) Platform SCIENCE BOOM --------------------- The Voyager science instrument boom carries the plasma detector, cosmic ray detector and the low energy charged particle detector. Platform SPACECRAFT BUS ----------------------- The basic structure of the spacecraft is called the 'bus', which carries the various engineering subsystems and scientific instruments. It is like a large ten-sided box. The centerline of the bus is called the z-axis (and thus the High Gain Antenna) points to Earth. The spacecraft is designed to roll about this axis by firing small thrusters which are attached to the bus. The thrusters are fueled by a liquid called hydrazine. Each of the ten sides of the bus contains a compartment (a bay) that houses various electronic assemblies. Bay 1, for example, contains the radio transmitters. The bays are numbered from 1 to 10 (numbered clockwise as see from Earth). Two additional turn axes, at right angles to the roll axis and to each other, are needed to give the spacecraft full maneuverability. These are the x-axis (pitch) and the y-axis (yaw). The booms supporting the nuclear power sources and the scan platform lie along the y-axis. " END_OBJECT = INSTRUMENT_HOST_INFORMATION OBJECT = INSTRUMENT_HOST_REFERENCE_INFO REFERENCE_KEY_ID = "MORRISON1982" END_OBJECT = INSTRUMENT_HOST_REFERENCE_INFO END_OBJECT = INSTRUMENT_HOST END