Final results from the space dust (SPADUS) instrument flown aboard the earth-orbiting ARGOS spacecraft

Abstract

In this paper, we present the final report of the data obtained from the Space Dust (SPADUS) instrument on the Earth-orbiting Advanced Research and Global Observation Satellite (ARGOS). The University of Chicago's SPADUS instrument on the US Air Force's Advanced Research and Global Observation Satellite has been operating in a nearly polar orbit, at an altitude of approximately 850 km, since soon after its launch on day 54, 1999 (23 February) until termination of the SPADUS operations on day 248, 2001 (5 September). The instrument consists of a polyvinylidene fluoride (PVDF) dust trajectory system, which includes two planar arrays of PVDF sensors (a total of 16 sensors per array) separated by 20.25 cm to provide time of flight (TOF) measurements. The trajectory system measures dust particle flux, mass distribution, velocity and trajectory. The instrument also includes the SPADUS Ancillary Diagnostic Sensor (ADS) subsystem, which measured energetic charged particles (electrons, protons, etc). The PVDF dust trajectory system detected a total of 368 dust impacts over the SPADUS live-time interval of 739 days, yielding an average particle flux of 0.50 impacts/day. Of these 368 impacts, 35 were D1–D2 type events—where particles impacted and penetrated a D1 sensor, then impacted a D2 rear array sensor—allowing for time-of-flight measurements. Of the 35 D1–D2 impacts on SPADUS, we identified 19 D1–D2 impacts yielding TOF values. Of these 19 events, 14 were ambiguous (either bound or interplanetary) and 5 were unambiguous interplanetary impacts. Examples of particle orbits for debris particles as well as D1–D2 impacts are detailed. We also describe transient particle streams detected by the SPADUS trajectory system, resulting from the passage of ARGOS through streams of debris particles in Earth orbit. One of the streams was shown to result from detection by SPADUS of the debris generated by the explosion of a Chinese booster rocket. The SPADUS flight data accumulated over the 30-month mission shows that PVDF-based dust instruments utilizing two planar arrays of PVDF dust sensors in a TOF arrangement—can provide useful measurements of particle velocity, mass distribution, flux, trajectory and particle orbital elements.