New TDRSS Communications Options for Small Satellites

David J. Zillig, Kenneth L. Perko
david.j.zillig.1@gsfc.nasa.gov
NASA/GSFC

Abstract:
New TDRSS Communications Options for Small Satellites

To expand the benefits and the use of the global TDRSS communications
infrastructure, NASA/GSFC is now embarking on a technology initiative to
bring new operations concepts and life cycle cost savings to the growing
small satellite community.  In the past, small spacecraft had problems using
the global TDRSS communications network due to the weight and power
consumption of the current user transponder hardware as well as the path
attenuation to geosynchronous orbit and the operational complexity and cost
of scheduling TDRSS service.

New hardware and  flexible operations concepts  for small spacecraft,
however, will greatly increase communications coverage and lower costs of
using TDRSS.  A new light weight, low power consumption 4th generation
S-Band transponder,  now under development,  will be capable of working with
TDRSS or ground terminals.  This will allow a mixed mode of operation where
a project can use TDRSS for command, housekeeping telemetry and tracking and
dump their high rate science data (2-3 Mb/sec) to a low-cost, receive-only
ground station. For projects  seeking the advantages of a total TDRSS
solution, the 4th generation S-Band transponder will provide an optional
K-Band signal source which, together with a K-Band phased array antenna, now
under development at GSFC, will allow a small satellite to  dump 2-3Mb/sec
of science data to TDRSS.

In addition, a  new demand access service to be incorporated in the TDRSS
Multiple Access  (MA) system will provide first-come, first-served access to
the forward link command channel and will also provide continuous return
link telemetry service.  This will eliminate scheduling MA service for
users, making flexible operations concepts possible, lowering mission
operations costs, and allowing receipt of random return transmissions and
service requests directly from the spacecraft whenever desired.