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STSS Demonstrator Mission

Tyneside, UK
2018 Apr 21
Saturday, Day 111

Maintained by:

STSS Demonstrator:


Description of missile detection and interception system

STSS Demonstrator home page
Which Satellite is Which?

Although the two satellite have been given Designations and Catalogue Numbers, the orbital elements are classified so none are being issued for public consumption. Two satellites have been detected transmitting from orbit, setting the challenge of identifying which is which.

This illustration from the satellite manufacturer shows how the two virtually-identical vehicles were stacked on the Delta for launch. On top is SV1, the first to be released. The cluster of instruments on the right-hand side of the lower satellite is the sensor used in its ballistic missile detection role.

STSS Stack

In its live coverage of the launch, "Spaceflight Now" described release of satellite 1 (SV1) being followed by a retrograde thruster firing by the Delta before it rotated 180 degrees and released satellite 2 (SV2). The effect of this was that SV1 was injected into an orbit slightly higher than the initial orbit of the Delta, while SV2's orbit was lower.

Due to its lower orbital period, SV2 very soon overtook SV1 and started to move ahead. Radio observations show two objects: the leading one, corresponding to SV2, transmitting at 2272.5 MHz and the other, SV1, transmitting at 2247.5 MHz.

The situation summarises as follows:

Catalogue Designation Name NORAD Name
359372009-052ASTSS Demonstrator SV1STSS DEMO 1 (USA 208)
359382009-052BSTSS Demonstrator SV2STSS DEMO 2 (USA 209)
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