Helium Magnetometer
A vector low-field helium magnetometer, not to be confused with the rubidium vapor or helium vapor magnetometer, was used to measure the interplanetary magnetic field. The three components of the field were measured essentially simultaneously but later transmitted sequentially. Each observation represented an average over approximately 1 s. The response dropped 3 dB for frequencies of 1 Hz, and higher frequency information was essentially lost. In each data frame, four vector measurements were made separated by intervals of 1.5, 0.9, and 2.4 s. The whole frame was repeated every 12.5 s. There was an uncertainty of plus or minus 0.35 nT per component. NSSDC has all the data from this experiment. Most of the data from this investigation was of the interplanetary region, but some data were obtained at Mars.