Atmospheric density uncertainty effects on the orbital lifetime estimation for CubeSats at LEO

Abstract

Nanosatellites, and especially CubeSats, at low earth orbits (LEOs) are a low cost option for monitoring atmospheric and environmental conditions around Earth. For instance, data for weather forecast reports can be obtained periodically with these kind of small satellites. Therefore, to academic institutions, universities, etc., this fact makes nanosatellites a very attractive way for researching with a moderate budget. In this project we compute orbital lifetimes (or simply lifetimes) for hypothetical missions involving nanosatellites at LEO, focusing our attention on exploring regions along the equatorial line. Thus, in the framework of orbital mechanics, we show the viability for these kind of missions in a long and a short term. Applications are projected for countries in northern South America, central Africa and islands/countries in southern Asia. To compute lifetimes, we take into account three effects: i) gravitational, ii) Earth deformations and iii) atmospheric density. These effects are included in the motion equation for a nanosatellite around Earth. After solving this equation for initial altitudes in 200-800 km above mean sea level (AMSL), we compute and report flight times to arrive at 150 km AMSL. These results are defined here as lifetimes and they are calculated for different atmospheric-density profiles according to experimental data and estimations. In conclusion, we find lowest and highest lifetimes for hypothetical missions involving small satellites at LEO orbiting along the equatorial line, and propose upper limits for density relative uncertainties in order to estimate reliable lifetimes.