Artificial Satellite Analysis Program (ASAP)
Program suited for studying planetary orbit missions including mapping and flyby components. Sample data included for geosynchronous station drift cycle study. Venus radar mapping strategy, frozen orbit about Mars, and repeat ground trace orbit. Written in FORTRAN.
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- "Artificial Satellite Analysis Program (ASAP) trajectory TABLE I Explosion altitudes above GEO Simulation Altitude above number GEO (km) 1 0 2 300 3 500 4 1000 5 2000 TABLE II Characteristics of the simulated fragmentation events Explosion epoch 11 May 1999 Explosion right ascension 298 • Explosion declination 0 • Fragments ≥ 1 mm 1733 Fragments ≥ 1 cm 1630 Fragments ≥ 10 cm 705 Maximum debris V 1 . 94 km s −1 predictor ( Kwok , 1987 "
ABSTRACT: The short- and long-term effects of spacecraft explosions, as a function of the end-of-life re-orbit altitude above the geostationary orbit (GEO), were analyzed in terms of their additional contribution to the debris flux in the GEO ring. The simulated debris clouds were propagated for 72 yrs, taking into account all the relevant orbital perturbations. The results obtained show that 6–7 additional explosions in GEO would be sufficient, in the long term, to double the current collision risk with sizable objects in GEO. Unfortunately, even if spacecraft were to re-orbit between 300 and 500 km above GEO, this would not significantly improve the situation. In fact, an altitude increase of at least 2000 km would have to be adopted to reduce by one order of magnitude the long-term risk of collision among geostationary satellites and explosion fragments. The optimal debris mitigation strategy should be a compromise between the reliability and effectiveness of spacecraft end-of-life passivation, the re-orbit altitude and the acceptable debris background in the GEO ring. However, for as long as the re-orbit altitudes currently used are less than 500 km above GEO, new spacecraft explosions must be avoided in order to preserve the geostationary environment over the long term.
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- "fragments larger than 1 mm, were propagated for 72 years with a modified, multiobject version of the ASAP numerical integrator developed at JPL (Kwok, 1987). The perturbations included were the geopotential (8 × 8 gravity field), the luni-solar attraction and the direct solar radiation pressure with eclipses. "
ABSTRACT: The effect of satellite breakups over 72 years, as a function of the end-of-life re-orbiting altitude (0–2000km), was analyzed in terms of fragment contribution to the object density in the geostationary orbit (GEO) ring, both in the short- and long-term. In the short-term, the explosions in GEO are the most detrimental for the GEO ring environment, though the average fragment density in the ring is never higher than 1/5 of the background, decreasing to less than 1/100 of the existing environment after 4 years (apart from a density rebound 5 decades later, due to luni-solar perturbations). Spacecraft end-of-life re-orbiting is a possible mitigation solution. But the re-orbiting altitude is critical if explosions continue to occur. In order to reduce the post-event average density by 1 order of magnitude with respect to an explosion occurring in GEO, more than 500km of re-orbiting is needed. Concerning the long-term environmental impact, the re-orbiting strategy supported by Inter-Agency Space Debris Coordination Committee (IADC) seems adequate to guarantee, after 2–3 years, a long-term average density of fragments in the GEO ring of at least 2 orders of magnitude below the existing background. But at least 1000km of re-orbiting are needed to stay below that threshold in the short-term too. In conclusion, the re-orbiting strategy recommended by IADC is totally adequate in the long-term, but only if satellite passivation is extensively carried out.
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ABSTRACT: An extensive calibration of semi-empirical atmospheric density models (JR-71, MSIS-86, MSISE-90, TD-88) was carried out, by analyzing the orbital decay of nine spherical satellites in the 200-1500 km altitude range. The orbital decay data used spanned a full solar activity cycle (1987-1999). The drag coefficients obtained by fitting the observed semimaior axis evolution with a high accuracy orbit propagator were compared with those estimated by theoretical analysis. MSIS-86 and MSISE-90, practically identical above 200 km, resulted to be the best models to compute air density below 400 km, in low solar activity conditions. However, JR-71 seemed more precise at greater altitudes and/or solar activity. TD-88 gave quite mixed results, but generally closer to JR-71. The intrinsic accuracy of JR-71, MSIS-86 and MSISE-90 was generally better than 20%, often better than 15% and, sometimes, close to 10%. But at altitudes greater than 400 km this picture resulted progressively degraded. A better drag coefficient theory and dedicated laboratory measurements will be needed to investigate in detail the deficiencies of the current models and improve the knowledge of the earth atmosphere with satellite drag analysis.
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