We discuss the characteristics of a SPACE DUST (SPADUS) instrument, based on polyvinylidene flouride (PVDF) dust sensors, which is being developed for flight on the USA near-Earth ARGOS mission to measure the flux, mass, velocity and trajectory of near-Earth dust. Natural (cosmic) dust is distinguished from man-made particles (orbital debris) by means of the velocity/trajectory information. SPADUS contains an Ancillary Diagnostic Sensor (ADS) for measurement of the flux, energy spectrum and pitch-angle distribution of energetic particles. The SPADUS sensors, measurement principles and performance are described and its role in the ARGOS mission is summarized.

In the near-Earth space, both man-made particles (orbital debris) and natural (cosmic) particles contribute to the particulate environment^1-6. Over the last several years, it has been recognized that the orbital debris component represents a serious and growing hazard to future space operations, both from the point of view of catastrophic collision, as well as erosive damage to critical surfaces (sensors, optics) resulting from long-term exposure to the smaller orbital debris particles^2,4. For interplanetary dust particles, it has been well recognized that the only means of determining their sources are by in situ velocity/trajectory measurements^1,7. Similarly, for near-Earth dust particles, velocity/trajectory measurements would provide the ability to discriminate between debris and natural particles¹. However, because of the limited exposure of velocity/trajectory sensors to near-Earth space up to the present time, the spatial distribution, mass spectrum, trajectory, and time variations of the small particle component (<1 cm diameter) of orbital debris have not been well determined^2,4.

Although the Long Duration Exposure Facility (LDEF)^5,6 did not carry a dust experiment which could have provided particle mass, velocity/trajectory information on a particle-by-particle basis, the Interplanetary Dust Experiment (IDE) carried by LDEF did provide nearly a year of spatio-temporal cumulative flux data which has shown that, at LDEF altitude, a majority of the particles in the size range from submicron to ~100 µm size are orbital debris and that a significant fraction of the debris particles are encountered as particle clouds⁸. Certainly, continuing analysis of the IDE data, as well as the crater and penetration feature morphologies on all of the other exposed LDEF surfaces^5,6 will yield important advances in our knowledge of the near-Earth particulate environment. However, at the present time, quantitative classification of LDEF impact particle types and their sources is just beginning to emerge⁹, and the present-day lack of quantitative measurements of the flux, mass distribution, velocity, and trajectory of small orbital debris particles continues to hamperdevelopment of reliable evolutionary modeling for orbital debris⁴, and detailed measurements of the characteristics of the orbital debris environment remain as an important goal in this field.

In this report, we describe a Space Dust (SPADUS) instrument which will address this need and which is currently under development for launch on the Advanced Research and Global Observation Satellite (ARGOS) in October, 1995. The SPADUS instrument will be jointly developed by groups at the University of Chicago (dust sensors and linear electronics), the Lockheed Space Sciences Laboratory (digital electronics and ADS system), and the Space Sciences Division of the Naval Research Laboratory (mechanical design and construction). The SPADUS instrument will be integrated and flown by the DOD Space Test Program. Funding for the University of Chicago portion of the SPADUS development was provided by the Office of Naval Research and NASA. In what follows, we present details of the design, test calibrations, and expected performance during flight of the SPADUS instrument and summarize the characteristics of the ARGOS mission.

References

1. Trajectory Determinations and Collection of Micrometeoroids on the Space Station, ed. F. Horz, LPI Tech. Rep. 86-05, Lunar and Planetary Institute, Houston (1986).
2. U.S. Congress, Office of Technology Assessment, Orbiting Debris: A Space Environmental Problem -- Background Paper, OTA-BP-ISC-72, Washington, DC; U.S. Government Printing Office (September 1990).
3. Proceedings of the Workshop on Hypervelocity Impacts in Space, University of Kent at Canterbury, in press (1992).
4. Proceddings of the Symposium on "Preservation of Near-Earth Space for Future Generations", University of Chicago, in press (1992).
5. LDEF -- 69 Months in Space: First LDEF Post-Retrieval Symposium, NASA CP 3134 (January 1992).
6. Second LDEF Post-Retrieval Symposium Abstracts Volume, NASA Conference Publication 10097 (June 1992).
7. Zook (Icarus).
8. J.D. Mulholland, J.P. Oliver, S.F. Singer, J.L. Weinberg, W.J. Cooke, N.L. Montague, P.C. Kassel, J.J. Wortman, W.H. Kinard and C.G. Simon, in: Proceedings of the Workshop on Hypervelocity Impacts in Space, University of Kent at Canterbury, in press (1992).
9. F. Horz and R. Bernhard, NASA Technical Memorandum 104750 (June 1992).