RB-Vapor and Fluxgate Magnetometers

Description

A dual gas rubidium alkali vapor instrument and two monaxial fluxgate magnetometers were designed to obtain vector magnetic field measurements of all three field components along a 1.8- to 42.6-earth radii trajectory traversing the geomagnetic field and extending into the interplanetary medium. The fluxgate magnetometers were oriented at an angle of 57 deg 45 min to the satellite spin axis and were placed on the ends of 79-cm booms to reduce to less than 1 nT the possibility of spacecraft magnetic field contamination. Data were transmitted to ground stations in periods of 126 s from the rubidium magnetometer and 3 s for each of the fluxgate magnetometers, in sequence with the other experiment transmissions. Performance was excellent, and data were obtained for 52 h. During launch, however, outgassing caused deposition of a film on the sphere containing the rubidium-vapor magnetometer. This increased the absorbency of the surface and raised the rubidium vapor magnetometer's temperature to 60 deg C after 2 h in sunlight, which interrupted the continuous operation of the magnetometer at 18 earth radii. Intermittent operation occurred for the next 6 h and this permitted inflight vector calibration of the fluxgate magnetometers in weak fields.