Comparison of disposal options for Tundra orbits in terms of delta-V cost and long-term collision risk

Abstract

Tundra orbits are inclined, moderately eccentric orbits with a 24-h period. These orbits undergo large excursions in eccentricity due to luni-solar gravity perturbations. For inclinations above 50°, eccentricity can grow to a value that causes perigee to reach the Earth's atmosphere, resulting in vehicle re-entry. In the current study, a range of potential disposal options for Tundra orbits were compared. Disposal options considered include moving to a disposal orbit near the Tundra mission orbit, lowering apogee just below GEO, and moving to near-circular orbits below and above GEO. Comparison metrics include delta-V cost (a measure of maneuver effort) and long-term collision risk. For the eccentric disposal orbit options, initial inclination and right ascension of ascending node (RAAN) were parametrically varied. For the near-circular disposal orbit options, initial argument of perigee and RAAN were parametrically varied. Study results indicate that a near-Tundra disposal orbit option appears to be the favorable selection since it has much lower delta-V cost than the other options and still has the second lowest overall collision risk, well below the threshold of 0.001 that is cited in U.S. standards on debris mitigation and space safety. In terms of orbital sustainability, for all RAAN values there are inclination values that enable re-entry within 200 years.