The Satellite Data System and the evolution of the EOI relay satellte in 60s-70s

[Jim]

Looks to be about the size of Leasat, no?

Just little longer

[Blackstar]

My SDS article will appear in The Space Review later today. It's just an update of my 2018 article, with some new information.

Although we have the basic program information (who built it, when, why, who managed it, etc.), we still don't have a lot of even basic details on the technology and hardware. For instance, I was told that SDS block 1 was based on the Intelsat IV bus, but the NRO has not confirmed that it was. I obtained documents many years ago about how many block 1 satellites were built, but I don't know how many were flown. This is complicated by the fact that an engineering test article was refurbished to serve as a backup satellite. Did it get launched or not? I don't know.

There are a lot of technical details we don't know, like how much power did the solar panels generate, how many antennas did the satellite have, etc.?

There are also some technical details that are probably really interesting (to certain people) that will probably not be revealed for a very long time. For instance, the KH-11 broadcast up to the SDS at one frequency, but the SDS broadcast down to the ground at a different frequency. Was this a difficult engineering task, or was it relatively straightforward?

[Blackstar]

https://thespacereview.com/article/4991/1

Spinning in the black: The Satellite Data System and real-time reconnaissance
by Dwayne A. Day
Monday, May 19, 2025

Next year marks the 50th anniversary of the launch of one of the most secretive communications satellites ever built, a satellite that received images from a reconnaissance satellite transmitted at a frequency that could not be detected from the ground, and then beamed them down to a ground station located outside of Washington, DC. Although many details of the satellite system remain secret to this day, enough is known about it to indicate that it was highly unusual, both in its design and the way it was developed.

This relay satellite, given the obscure name of Satellite Data System, or SDS for short, was developed under a unique management arrangement. Although it carried a highly classified mission payload—“black” in the jargon of the intelligence community—the satellite itself was developed and procured by the unclassified—“white”—Air Force Space and Missile Systems Office, thus straddling the edge of the shadowy world of satellite reconnaissance, with one foot in the light and the other in the shadows. A declassified history by Vance O. Mitchell, “The NRO, the Air Force, and the First Reconnaissance Relay Satellite System, 1969-1983,” describes how this unusual management relationship was developed—and almost fell apart—during its early years.

[Michael Cassutt]

I just compared the 2012 release to the 2024 release. The only new bits are:

KENNEN
ZAMAN
ZOSTER
Hughes

But I'm pretty sure that all those were revealed in a release a few years ago, so there's nothing new in the 2024 release.

What is disappointing is that they could have released a bit more about the orbits. They've already indicated that the highly-elliptical orbit was used.

One page mentions the addition of a third secondary payload. I cannot remember what that was. Anybody have any ideas?

I'm not sure if I've mentioned this, or someone else has, but filling in (with high confidence) two redacted names in the SDS history . . . the SAMSO SPO Director was Col. Richard Drennan, USAF. The Program B manager was, I believe, Jack Maxey (not the individual you will find most often if you Google him).

Michael Cassutt

[Blackstar]

What document is this from? It's at the beginning of this thread but comes from one of the EOI documents.

[Skyrocket]

What document is this from? It's at the beginning of this thread but comes from one of the EOI documents.

It is from this one, an historical compilation titled "Declassification of Historically Significant Documents: NRO 60th Anniversary" (document reference SC-2021-00002_C05097836)

https://www.nro.gov/Portals/65/documents/foia/declass/HISTORICALLY%20SIGNIFICANT%20DOCs/NRO%2060th%20Anniversary%20Docs/SC-2021-00002_C05097836.pdf

[LittleBird]

What document is this from? It's at the beginning of this thread but comes from one of the EOI documents.

It is from this one, an historical compilation titled "Declassification of Historically Significant Documents: NRO 60th Anniversary" (document reference SC-2021-00002_C05097836)

https://www.nro.gov/Portals/65/documents/foia/declass/HISTORICALLY%20SIGNIFICANT%20DOCs/NRO%2060th%20Anniversary%20Docs/SC-2021-00002_C05097836.pdf

I've always felt it must be part of what would essentially be "the KENNEN Story", analogous to the volumes on GAMBIT and HEXAGON. I hope to live long enough to see the rest of it, and even the 1st generation GEO sigint birds, though I'm not holding my breath.

[Blackstar]

What document is this from? It's at the beginning of this thread but comes from one of the EOI documents.

It is from this one, an historical compilation titled "Declassification of Historically Significant Documents: NRO 60th Anniversary" (document reference SC-2021-00002_C05097836)

https://www.nro.gov/Portals/65/documents/foia/declass/HISTORICALLY%20SIGNIFICANT%20DOCs/NRO%2060th%20Anniversary%20Docs/SC-2021-00002_C05097836.pdf

Thank you. Somebody asked me for the original source and I couldn't remember it. They are writing a history on global communications.