Ka-Band for CubeSats

As 3U and 6U CubeSat missions begin to play a fundamental role in space science, advanced applications and even commercial utilization, there is a strong corresponding demand for higher data rates from even smaller fractions of the volume of a CubSsat envelope. Based on a concept outlined at this conference in 2012, a Ka-Band transmitter for Earth Exploration applications has now been developed and tested and this RF technology is now in-orbit; flying as a major demonstration in a 6U spacecraft. Since this technology is capable of providing tens of GBytes per day of downlinked data from a single 3U, 6U or 12U CubeSat system, the future is even brighter. We will review in this presentation what has been accomplished to date, the challenges associated with using Ka-Band and where this technology is headed in the immediate future. This paper also demonstrates the effectiveness of Ka-Band for satellite interlinks (space-to-space relay) and the ultimate advantage of Millimeter Wave ( mmW) technology to deep space communications using very small systems. A less obvious advantage of Ka-Band: improved spectrum management via spot beam frequency reuse is also of prime importance to the community. This aspect of mmW technology will also be examined and a plan for future spectrum utilization will be outlined. THE PAST AND AN UPDATE FROM 2012 At the SmallSat Conference in 2012 one of the authors (King) presented a systems paper forecasting the importance of mmW communications to the small satellite community, with a particular emphasis given to very small spacecraft (NanoSats and/or CubeSats). [1] While large remote sensing satellites are not disappearing quite as fast as anticipated by that paper, the cost vs. performance difference between big and small is becoming painfully evident as small system performance continues to improve apace, while large remote sensing satellites are becoming even more expensive than they were in 2012. It still remains just a matter of time before big systems must give way to lower cost more effective solutions. In that paper we also called attention to the realization that even NanoSat sized systems (3U and up) are beginning to play an ever-increasing role in the science and commercial worlds. And, they will be successful, provided that attention is paid to the limiting factor associated with these missions – data throughput. In that regard, nothing has really changed in three years except the reality of the throughput limitation has gone from being a partially kept secret to a commonly understood reality within the community. If we allow that the term “CubeSat” implies systems as large as 16U (as vendors of P-PODs are now manufacturing components up to this size) the limitation of diffraction for CubeSat optics is not an issue for commercial quality imagery (2m GSD and above). Advances in focal plane arrays more likely set the current optical limitation and for LEO systems, simple math quickly shows that if wide area, high resolution coverage is a system goal, the limitation, by a large margin, is data throughput. In the previous paper we clearly identified 1) data rate and 2) mutually exclusive ground station access as the two critical components defining throughput in the LEO world. And, while the number of ground stations supporting a network might vary by a factor of 10 as a practical matter, the data rate supported by a small satellite system can vary by as much as a factor of between 1000 and 10,000 times. It is worth re-