NASA's space communications and navigation (scan) program is investigating potential options for providing communications services simultaneously to multiple user missions in low earth orbit (LEO) via…

This is a firm fixed-price delivery order awarded by NASA's Glenn Research Center to Northrop Grumman Systems Corporation, through its Military Aircraft Systems division doing business as Aerospace Systems. The $154,322 contract is part of the larger Research and Technologies for Aerospace Propulsion Systems 2 (RTAPS2) indefinite delivery/indefinite quantity (IDIQ) contract.

The purpose of this study is to evaluate the potential of electronically steered or switched multiple beam antenna systems to provide advanced multiple access communications services in the Ka-band frequency for NASA's Space Communications and Navigation (SCAN) program. The study will explore techniques such as direct phased arrays, phased array-fed reflectors, and multiple simultaneous spot beams that can provide communications services to multiple user missions in low Earth orbit. Key considerations include balancing the communications link burden between the relay satellite and user missions, as well as achieving the desired antenna gain-to-noise temperature ratio (G/T) performance.

NASA's space communications and navigation (scan) program is investigating potential options for providing communications services simultaneously to multiple user missions in low earth orbit (LEO) via advanced multiple beam and multiple access (MB/MA) techniques. These are being explored for potential use on future near-earth communications relay satellites in geosynchronous earth orbit (GEO). Options of interest in this study are advanced alternatives to service provision techniques used on the current tracking and data relay satellites (tdrs). Those are s-band multiple access (SMA) via phased array with ground-based beam-forming, and s-band and KA-band single access (SSA and kasa) via by mechanically steered parabolic dishes. KU-band single access service is expected to end with the current fleet of tdrss. The purpose of this study is to evaluate the potential of electronically steered or switched multiple beam antenna systems to provide advanced multiple access services in KA-band. MB/MA antennas under consideration in this study are: (1) direct phased arrays (possibly separate transmit and receive arrays) providing multiple simultaneous electronically-steered beams; (2) phased array-FED reflectors that use a reflector to increase the array's gain while maintaining the required field of regard (for) (note that this is different from a confocal-FED phased array concept); and (3) and multiple simultaneous spot beams where spot beams are electronically switched to track user missions and the user mission hand-offs are handled onboard the relay. In all three cases, beam-forming, beam steering or switching, and controlling is performed onboard the relay satellite. IT is important to note that hand-offs of user missions between spot beams and the need for directional beams on user mission spacecraft have been assumed to impose additional, unwanted user burden by some in the scan program. The KA-band space-to-space spectrum allocation for science use has more than sufficient bandwidth (1.5 GHZ) to accommodate any projected aggregate NASA mission use. Candidate MB/MA techniques identified by the offeror should consider partitioning or channelizing the available spectrum into a low-data rate multi-user service similar to the current SMA spread spectrum functionality, and a flexible spectrum channelization and multiple access technique for higher data rate users that could potentially serve multiple high data-rate users at once depending on data needs. A key concern for this study is balancing between the communications link burden between the relay satellite and the user missions. Many of the current tdrs users access the SSA service via omni-directional antennas to provide low data-rate (1-8 kbps) tracking, telemetry and control (TT & c) functionality. Future users with similar needs would require a higher relay g/t than tdrs SMA for the future relay MB/MA payload to provide these same services via a KA-band omni antenna on the user mission spacecraft. Or, the user would need to incorporate a higher gain, steerable antenna of some form. Alternatives for KA-band user mission antennas is the topic of a separate RTAPS2 task order study contract. Finally, the 2ND and 3RD generation tdrs kasa systems have a relatively high KA-band g/t, and have set expectations for future relay systems. Achieving the desired g/t may be prohibitively difficult for some of the future candidate solutions. Therefore this study should also investigate lower performance MB/MA solutions as options. Lower receiver g/t on the relay with increased user burden for eirp is one possibility.