Data Set Information
DATA_SET_NAME VEGA2 DUST PARTICLE IMPACT DETECTOR DATA V1.0
DATA_SET_ID VEGA2-C-SP2-2-RDR-HALLEY-V1.0
NSSDC_DATA_SET_ID
DATA_SET_TERSE_DESCRIPTION
DATA_SET_DESCRIPTION Data Set Overview: The SP-2 experiment on Vega spacecraft was intended for studying the spatial and mass distributions of dust particles in the cometary coma over the mass range 1.e-16 to 1.e-6 g. Covering such a broad mass range was made possible by using sensors of two types, namely, impact plasma and acoustic. The threshold sensitivity of the dust particle acoustic detector in terms of the transferred momentum is given by Pmin ~ 2x10**-5 gcm/s. Taking into account that the recoil momentum may exceed the particle momentum mV by 5 to 10 times, the minimum mass of recorded particles is < 3x10**-13 g. The measurement range n (> m)x3x10**-13 to ~ 2x10**-6 g is divided into 16 channels. With the relative width delta/m ~ 2.82, sensitive area S : 500 cm**2, accumulation time for one spectrum is 1 s, which corresponds to the spatial resolution ~ 80 km over the flyby trajectory. The counting rate of small mass particles is about 4095 1/s. The ionization detector is capable of recording particles with mass 3x10**-16 to 3x10**-11g. The number of channels is 6, with relative width delta/m : 10, sensitive area - 40 cm**2. The limit counting rate of small mass particles is ~ 65,500 1/s. The accumulation time for one spectrum is 1 s. The flyby trajectories of the Vega spacecraft in the cometocentric frame can be specified by the coordinates of the closest approach to the nucleus R0(R0x,R0y,R0z) and the components of the relative velocity V(Vx,Vy,Vz). The corresponding values for Vega1 and Vega2 were as follows: Vega 1: R0x : 7830 km; R0y : 2480 km; R0z : 3400 km; Vx : 28.64 km/s; Vy : -72.73 km/s; Vz :-12.95km/s; Vega 2: R0x : 7100 km; R0y : 2680 km; R0z : 2630 km; Vx : 30.53 km/s; Vy : -69.44 km/s; Vz :-11.88km/s; If the results of the dust flux measurements are referred to the time reckoned from the instant of closest approach, the corresponding distances to the cometary nucleus can be found as R:R0*sqrt(1 + (t/t0)^2), where the parameter t0 : R0/V. In the course of measurements the numbers of particle impacts with masses exceeding the channel threshold is counted in each pulse height channel at 1 second intervals along the trajectory: N(>m) : F(>m)*S*T : n(>m)*V*S*T, where n(>m) is the number density, F(>m):n(>m)*V the cumulative flux, S the effective sensor area (500 cm2 for the acoustic sensor and 28.57 cm2 for the impact plasma one), T:63/64s the accumulation time in each measurement. The data for Vega2 (submitted by Dyachkov at IKI)contains time of measurement referred to one of closest approach, 5 columns of impact plasma sensor data, and finally 14 columns of acoustic sensor data, for a total of 20 columns. Total number of records is 2267. For the acoustic sensors, dead time corrections were introduced at channel count rate N(>m) > 50/s. For the fast impact plasma sensors such corrections were not needed.
DATA_SET_RELEASE_DATE 3000-01-01T00:00:00.000Z
START_TIME 1986-03-09T06:29:22.000Z
STOP_TIME 1986-03-09T07:42:32.000Z
MISSION_NAME VEGA 2
MISSION_START_DATE 1984-12-21T12:00:00.000Z
MISSION_STOP_DATE 1986-04-01T12:00:00.000Z
TARGET_NAME HALLEY
TARGET_TYPE COMET
INSTRUMENT_HOST_ID VEGA2
INSTRUMENT_NAME DUST PARTICLE DETECTOR
INSTRUMENT_ID SP2
INSTRUMENT_TYPE ACOUSTIC SENSOR
NODE_NAME Small Bodies
ARCHIVE_STATUS ARCHIVED
CONFIDENCE_LEVEL_NOTE Confidence Level Overview: N/A
CITATION_DESCRIPTION Dyachkov, A. V., VEGA2 DUST PARTICLE IMPACT DETECTOR DATA V1.0, VEGA2-C-SP2-2-RDR-HALLEY-V1.0, NASA Planetary Data System, 1997
ABSTRACT_TEXT The SP-2 experiment on Vega spacecraft was intended for studying the spatial and mass distributions of dust particles in the cometary coma over the mass range 1.e-16 to 1.e-6 g. Covering such a broad mass range was made possible by using sensors of two types, namely, impact plasma and acoustic.
PRODUCER_FULL_NAME INTERNATIONAL HALLEY WATCH
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