/********************** INSTHOST TEMPLATE ***********************************/ OBJECT = INSTRUMENT_HOST INSTRUMENT_HOST_ID = PVO OBJECT = INSTRUMENT_HOST_INFORMATION INSTRUMENT_HOST_NAME = "PIONEER VENUS ORBITER" INSTRUMENT_HOST_TYPE = SPACECRAFT INSTRUMENT_HOST_DESC = " \v Instrument Host Overview ======================== The Pioneer Venus mission objectives dictated the requirement for two spacecraft designs designated the Orbiter and the Multiprobe. (The Multiprobe is defined as the Bus with the one Large Probe and three identical Small Probes attached in the launch/cruise configuration.) The conceptual designs of these spacecraft resulted from Phase B studies conducted from October 1972 to July 1973, and after selection of the spacecraft contractor, Hughes Aircraft Company, in February 1974, a spacecraft conceptual design review was conducted in November 1974. The Orbiter and Multiprobe utilized the same designs to the maximum extent possible to minimize costs. In addition, designs of subsystems or portions of subsystems from previous spacecraft designs (such as OSO and Intelsat) were utilized to the maximum extent possible with little or no modifications. This commonality in the two spacecraft designs also resulted in certain amounts of commonality in ground test equipment and test software as well as commonality in spacecraft flight operations and associated software. [ Extracted from: Nothwang, George J., `Pioneer Venus Spacecraft Design and Operation', IEEE Transactions on Geoscience and Remote Sensing, vol. GE-18, No. 1, January 1980]. The main body of the spacecraft is a flat cylinder 2.5 meters in diameter and 1.2 meters high. In the upper end of this cylinder there is a circular equipment shelf with an area of 4.37 square meters on which all the scientific instruments and electronic subsystems are mounted. The shelf is mounted on the forward end of a thrust tube that connects the spacecraft to the launch vehicle. Below the shelf, 15 thermal louvers control heat radiation from an equipment compartment located between the shelf and the top of the spacecraft. A cylindrical solar array attached to the shelf by 24 brackets forms the circumference of the flat cylinder of the spacecraft. The spacecraft spins about its cylindrical axis wit ha nominal spin period of 12 seconds. On top of the spacecraft, a 1.09 meter diameter, despun, high-gain, parabolic dish antenna is mounted on a mast so that its line of sight clears equipment mounted outside the spacecraft. The despun design allows the antenna to be mechanically directed to Earth from the spinning spacecraft. The antenna operates at S- and X-bands. The spacecraft also carries a solid propellant rocket motor. Including the antenna mast, the Orbiter is almost 4.5 meters high, and it weighed 553 kg when launched. The launch weight included 45 kg of scientific instruments and 179 kg of rocket propellant. Orbital Characteristics: (Table 5-6, p150, Fimmel et al, 1995) Parameter Value __________________________________________________________ Periapsis, km (miles) 150-200 (93-124) Apoapsis, km (miles 66,900 (41,572) Eccentricity 0.842 Average period, hr 24.03 Inclination to Equator, deg 105.6 Periapsis Latitude 17.0 N Periapsis Longitude, deg (orbit 5) 170.2 E __________________________________________________________ Platform Descriptions ===================== MAGNETOMETER BOOM ----------------- An 4.8 meter long boom (188.9 inches) that was unfurled and extended automatically after launch. The magnetometer boom is located 240 degrees from the X-axis of the spacecraft coordinate system, measured in towards the Y-axis (in the spin direction) of the spin plane (XY). The total distance from the end of the boom to the orbiter spin axis is 5.94 meters (234.0 inches). \v " END_OBJECT = INSTRUMENT_HOST_INFORMATION OBJECT = INSTRUMENT_HOST_REFERENCE_INFO REFERENCE_KEY_ID = NOTHWANG1980 END_OBJECT = INSTRUMENT_HOST_REFERENCE_INFO OBJECT = INSTRUMENT_HOST_REFERENCE_INFO REFERENCE_KEY_ID = FIMMELETAL1995 END_OBJECT = INSTRUMENT_HOST_REFERENCE_INFO END_OBJECT = INSTRUMENT_HOST /**********************MP INSTHOST TEMPLATE ***********************************/ OBJECT = INSTRUMENT_HOST INSTRUMENT_HOST_ID = PVMP OBJECT = INSTRUMENT_HOST_INFORMATION INSTRUMENT_HOST_NAME = "PIONEER VENUS MULTIPROBE" INSTRUMENT_HOST_TYPE = "SPACECRAFT" INSTRUMENT_HOST_DESC = " \v Instrument Host Overview ======================== Mass: 290 kg (bus), 315 kg (large probe), 90 kg (each small probe) Power System: Solar Array of 241 W (bus), Batteries (probes) The Pioneer Venus Multiprobe consisted of a bus which carried one large and three small atmospheric probes. The large probe was released on November 16, 1978 and the three small probes on November 20. All four probes entered the Venus atmosphere on December 9, followed by the bus. The Pioneer Venus large probe was equipped with 7 science experiments, contained within a sealed spherical pressure vessel. This pressure vessel was encased in a nose cone and aft protective cover. After deceleration from initial atmospheric entry at about 11.5 km/s near the equator on the Venus night side, a parachute was deployed at 47 km altitude. The large probe was about 1.5 m in diameter and the pressure vessel itself was 73.2 cm in diameter. The science experiments were: * a neutral mass spectrometer to measure the atmospheric composition * a gas chromatograph to measure the atmospheric composition * a solar flux radiometer to measure solar flux penetration in the atmosphere * an infrared radiometer to measure distribution of infrared radiation * a cloud particle size spectrometer to measure particle size and shape * a nephelometer to search for cloud particles * temperature, pressure, and acceleration sensors The three small probes were identical to each other, 0.8 m in diameter. These probes also consisted of spherical pressure vessels surrounded by an aeroshell, but unlike the large probe, they had no parachutes and the aeroshells did not separate from the probe. Each small probe carried a nephelometer and temperature, pressure, and acceleration sensors, as well as a net flux radiometer experiment to map the distribution of sources and sinks of radiative energy in the atmosphere. The radio signals from all four probes were also used to characterize the winds, turbulence, and propagation in the atmosphere. The small probes were each targeted at different parts of the planet and were named accordingly. The North probe entered the atmosphere at about 60 degrees north latitude on the day side. The night probe entered on the night side. The day probe entered well into the day side, and was the only one of the four probes which continued to send radio signals back after impact, for over an hour. More detailed information on the probes is available. The Pioneer Venus bus also carried two experiments, a neutral mass spectrometer and an ion mass spectrometer to study the composition of the atmosphere. With no heat shield or parachute, the bus survived and made measurements only to about 110 km altitude before burning up. The bus was a 2.5 m diameter cylinder weighing 290 kg, and afforded us our only direct view of the upper Venus atmosphere, as the probes did not begin making direct measurements until they had decelerated lower in the atmosphere. Probe Entry Timing Events: (Table 5-2, p141, Fimmel et al, 1995) Time at Spacecraft, hr:min:sec* - PST - Dec 9, 1978 _______________________________________________________________ Parameter Large North Day Night _______________________________________________________________ End of coast 10:24:26 10:27:57 10:30:27 10:34:08 Initiate telemetry 10:29:27 10:32:55 10:35:27 10:39:08 200 km entry 10:45:32 10:49:40 10:52:18 10:56:13 Radio blackout begin 10:45:53 10:49:58 10:52:40 10:56:27 Signal locked on 10:46:55 10:50:55 10:53:46 10:57:48 Jettison parachute 11:03:28 N/A N/A N/A Impact with surface 11:39:53 11:42:40 11:47:59 11:52:05 Signal ended 11:39:53 11:42:40 12:55:34 11:52:07 Bus Entry 12:12:52 Bus signal ended 12:22:55 _______________________________________________________________ Event Duration _______________________________________________________________ Descent time 54:21 53:00 55:41 55:52 Blackout time 01:02 00:57 01:06 01:21 Time on parachute ~17:07 N/A N/A N/A Surface operations none none 01:07:37 00:02 * Earth receive times were approximately 3 minutes later Probe Entry Impacts: (Table 5-3, p144, Fimmel et al, 1995) _______________________________________________________________ Probe Latitude Longitude Solar-Zenith-Angle Venus Local deg E. deg (SZA) deg Time hr:mm _______________________________________________________________ Large 4.4 N 304.0 65.7 07:38 North 59.3 N 4.8 108.0 03:35 Day 31.3 S 317.0 79.9 06:46 Night 28.7 S 56.7 150.7 00:07 _______________________________________________________________ Bus Entry and Location of Sun and Earth: (Table 5-4, p144, Fimmel et al, 1995) _______________________________________________________________ Probe Lat E.Lon SZA Local Time deg deg deg hr:mm _______________________________________________________________ Bus entry at 200 km 37.9 S 290.9 60.7 08:30 Subsolar 0.5 S 328.5 0 12:00 Sub-Earth 1.6 S 1.7 123.1 03:47 ______________________________________________________________ Probe Anomalies: (Table 5-5, p146 Fimmel et al, 1995) ____________________________________________________________________ Anomaly Large North Day Night ____________________________________________________________________ Apparent failure of temperature sensors X X X X Apparent failure of net flux radiometer fluxplate temperature sensors X X X Abrupt changes and spikes in the data from the net flux radiometer X X X Change in the indicated deployment status of the atmospheric structure temperature sensor and net flux radiometer booms X X X Erratic data from two thermocouples embedded in the heat-shield X X X Erratic data from a thermistor measuring junction temperature of the heat-shield thermocouples. X X X Slight variation in the current and voltage levels in the power bus X X X Abrupt changes in the cloud particle size laser alignment monitor X N/A N/A N/A Decrease in the intensity of the beam returned to the cloud particle size spectrometer X N/A N/A N/A Noise spikes in the infrared radiometer X N/A N/A N/A Spikes in the data monitoring the ion pump current of the mass spectrometer analyzer X N/A N/A N/A Spurious reading from the thermocouples when the heat shield was dropped from the probe X N/A N/A N/A ____________________________________________________________________ \v " END_OBJECT = INSTRUMENT_HOST_INFORMATION OBJECT = INSTRUMENT_HOST_REFERENCE_INFO REFERENCE_KEY_ID = "N/A" END_OBJECT = INSTRUMENT_HOST_REFERENCE_INFO END_OBJECT = INSTRUMENT_HOST