Needle in a Haystack: Finding Two S-band CubeSats in a Swarm of 64 Within 24 Hours

In the past few years we have witnessed the ascension of rideshare missions, breaking records again and again for the total number of satellites released on a single launch. Such large swarms of spacecraft make it difficult for the Combined Space Operations Center (CSpOC) to identify satellite orbits until days to weeks after launch. For the SSO-A launch in December 2018, it took 11 days to catalog all 64 objects. While satellites should be designed to survive without ground contact for that long, for most missions, making contact and assessing vehicle state of health during early orbit operations is critical, and waiting for object cataloging is simply too risky. Furthermore, as CubeSats take on more operational roles, the amount of data needed to both uplink and downlink requires moving away from the traditional L-band frequencies to S-band and higher. While higher frequency bands allow faster data transmission it comes at a cost of smaller ground antenna footprints, requiring an order of magnitude better pointing knowledge in order to establish communications lock. With typical canister ejection speeds, spacecraft can drift away from the launch vehicle, whose orbit is typically known and provided by the launch integrator. Depending on ground antenna size, this implies the spacecraft will no longer be in the ground antenna field of view within a day or so of launch. This makes establishing communications with the spacecraft within the first 24 hours after launch paramount. This paper discusses how the ORS-7/DHS Polar Scout mission successfully achieved contact with its two 6U CubeSats and determined their orbital ephemerides in less than 24 hours after launching on the SSO-A mission on December 3, 2018. We present our spacecraft acquisition plan, which encompassed a number of different strategies that can be employed depending on the capabilities and equipment at the ground site

Design and Analysis of on-Orbit Servicing Architectures for the Global Positioning System Constellation

Satellites are the only major Air Force systems with no maintenance, routine repair, or upgrade capability. The result is expensive satellites and a heavy reliance on access to space. At the same time, satellite design is maturing and reducing the cost to produce satellites with longer design lives. This works against the ability to keep the technology on satellites current without frequent replacement of those satellites. The Global Positioning System Joint Program Office realizes that it must change its mode of operations to quickly meet new requirements while minimizing cost. The possibility of using robotic servicing architectures to solve these problems is considered in this thesis. The authors accomplished this through a systems engineering and decision analysis approach in which a number of different alternatives for on-orbit satellite repair and upgrade were analyzed. This approach involved defining the problem framework and desired user benefits, then developing different system architectures and determining their performance with regard to the specified benefits. Finally, the authors used decision analysis to evaluate the alternative architectures in the context of the user\u27s goals. The results indicate favorable benefit-to-cost relationships for on-orbit servicing architectures as compared to the current mode of operation