Slot Architecture for Separating Satellites in Sun-Synchronous Orbits

Abstract

A slot architecture is developed for separating satellites in congested Sun-synchronous orbits that are a limited natural resource in low Earth orbit. A key feature of the slot architecture is a phasing rule that provides sufficient separation between slots in the vicinity of their orbital crossing points. Other features involve the discretization of orbital parameters such as semi-major axis and right ascension of the ascending node. The design parameters of the slot architecture were selected with detailed consideration of various operational aspects and orbital perturbations. A preliminary analysis indicates that slotmaintenance requirements are automatically satisfied by maneuvers that are routinely performed by current high-value Earth observation satellites to satisfy their existing mission objectives. A simulation analysis of satellites currently in Sun-synchronous orbit confirms that implementation of the proposed slot architecture would greatly reduce the frequency of close approaches between these satellites.

Global communication coverage using Cubesats

“…Currently, space engineers conduct conjunction analysis for LEO satellites with a 25 km x 25 km x 2 km box [12]. The International Space Station has a more stringent requirement whereby maneuvers will be performed when space objects come close to the operation box of 25 km x 25 km x 0.75 km for orbits at the attitude between 330 km to 435 km [13].…”

Characterization of the Effects of a Sun-Synchronous Orbit Slot Architecture on the Earth's Orbital Debris Environment

“…Close approaches, often referred to as conjunctions, are not uncommon among LEO satellites and commonly result in avoidance maneuvers. Past research has been done into an approach to keep this regime better separated both horizontally [2,7] and vertically. [8] Chapter 2 reviews a portion of this effort.…”

“…[5,6] Consider, then, that with 44% of LEO satellites in SSO, [2] the region is a popular choice for mission designers and may soon become overcrowded. Compound this with the fact that collision probabilities are greatest when the sum of two satellites' inclinations is near 180˝, [1] as is the case for SSOs, and the risk of collision becomes quite high among this class of satellites.…”

“…[2] Sun-synchronous orbit is achieved by exploiting the perturbing effect of J 2 on Ω, right ascension of the ascending node (RAAN). [5] A satellite is in SSO if its nodal rate matches the average rate of the Sun's motion around the Earth, i.e., when…”

“…[1] Today, there are more than a thousand active satellites, over 22,000 debris objects with characteristic length greater than 10 cm, and millions of smaller pieces of debris in Earth orbit. [2] Nearly 50% of the active satellites and a majority of debris objects are in low Earth orbit (LEO), i.e. in an orbit below 2000 km altitude.…”