Polar Satellites: Satellite Data System and Package D

There are two programs of classified-host satellites that provide support for AFSATCOM payloads: the Satellite Data System (SDS) and Package D.

These satellites provide UHF SATCOM communications for the users in the polar regions where communications using other more equatorial-based satellites are difficult, if not impossible. The SATCOM Management Center receives orbital information for the available polar satellites and then determines appropriate times for the AFSATCOM payloads onboard these satellites to be enabled or disabled.

Satellite Data System: SDS satellites include a payload similar to the 12-channel AFSATCOM 5 kHz system onboard the FLTSATs, with the exception that all 12 channels are regenerative and support only 75 bps customers. EAM functions are the same and channels one through seven can frequency hop. There are no non-regenerative channels, 5, 25, or 500 kHz, available on the SDS satellites.

Package D: The Package D satellites provide a UHF package identical to the SDS satellites, with the exception that the first 10 channels can frequency-hop versus the first seven on the FLTSATCOM and SDS satellites.

In addition, Package D satellites include an SCT payload similar to that onboard the DSCS-III satellites, and allow an SHF uplink. The Package D SCT does not provide an SHF downlink, however, and transmits only at UHF.