Author(s): DaveBowman2001

Release date:

The Satellite Data System is a fleet of communication relay satellites for transmitting real-time data from US spy satellites (e.g. KH-11) in Molniya-type orbits. This addon covers the four second-generation satellites launched between 1989 and 1996, each have an expected design life of 8 years. The first three were launched in one of the last military Shuttle missions in history


  • Requires the Space Shuttle addon installed to allow the first three satellites of this addon to appear on Celestia
  • Orbital data for all four satellites are semifictional as they have no TLEs recorded from CelesTrak due to their classified military nature
  • Shuttle missions STS-28, STS-38, and STS-53 will be modified by this addon upon installation

A fully deployed SDS-2/Quasar satellite in orbit

Satellite Data System
Mission Start End
Second generation, 1989-1996
Quasar 8 (USA-40) 1989-Aug-81997?
SDS 2-1, launched from STS-28 (Columbia)
Quasar 9 (USA-67) 1990-Nov-111998?
SDS 2-2, launched from STS-38 (Atlantis) with Prowler
Quasar 10 (USA-89) 1992-Dec-22000?
SDS 2-3, launched from STS-53 (Discovery). Also the last military satellite to be deployed from a Space Shuttle
Quasar 11 (USA-125) 1996-Jul-32004?
SDS 2-4, launched from a Titan IV-A rocket
Timeline of SDS-2/Quasar satellites

STS-28 (Columbia)

STS-38 (Atlantis)

STS-53 (Discovery)

Open in Celestia (Recommended) or Download

How to install add-ons? Find out here.