General
TDRSS services are designated as Forward or Return, Multiple Access (MA), or
Single Access (SA). This introduction provides a brief definition of those TDRSS
services.
TDRSS Forward Services
TDRSS forward service is defined as a communication path which generally
originates at the customer control center and is routed through the Tracking and
Data Relay Satellite (TDRS) to the customer's orbiting spacecraft. Typically,
the forward service is utilized for customer spacecraft commanding. Forward
service data rates are variable depending on the selection of SA or MA service
utilization as well as specified frequency (K band or S band). Detailed forward
service information is contained in the TDRSS Data
Rates and the Data Rates Notes and Restrictions
portion of the knowledge base.
TDRSS Return Services
TDRSS return service is defined as the communication path which generally
originates at the customer spacecraft and is routed through TDRS back to the
customer control center or data acquisition location. Typically, the return
service is utilized for the return of science data and spacecraft status
information. Return service data rates are variable depending on the selection
of SA or MA service utilization as well as specified frequency (Ku , Ka or S
band). Detailed return service information is contained in the
TDRSS Data Rates and theData Rates Notes and
Restrictions portion of the knowledge base.
Multiple Access Service
The MA service provides dedicated return service to low earth orbiting customer
spacecraft with real-time, playback, and science data rates up to 100 kbps.
Return service support can be provided for up to five simultaneous customers per
TDRS at a time. Forward service operations are time shared with a maximum
individual customer data rate of 10 kbps and will support one customer per TDRS
at a time. The MA service operates at S band (fixed frequency and polarization).
Single Access Service
Four SA services are available through each TDRS SA antenna:
- S band single access forward (SSAF)
- S band single access return (SSAR)
- K band single access forward (KSAF)
- K band single access return (KSAR)
Forward service operation supports data rates to 300 kbps at SSAF and to 25 Mbps
at KSAF. Return service operations are supported at data rates to six Mbps at
SSAR (rate 1/2 coded) and 300 Mbps (uncoded) KSAR.
A list of frequently asked questions regarding TDRSS telecommunications is
provided for quick reference
A tabular summary of the services is presented below:
Detailed information is available on the following topics:
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