The Atlas SLV-3 was a stage and a half rocket, built as a standardised replacement for earlier Atlas launch systems, which had been derived from the various Atlas missiles. A Burner upper stage was flown on the final flight to increase payload.
ATDA in orbit, with its payload fairing still attached.
It is most well known for launching the Augmented Target Docking Adapter (ATDA), a backup for the Gemini Agena Target Vehicle which was to be used by Gemini 9 after its GATV failed to reach orbit. The launch was conducted on 1 June 1966, and was the first flight of the Atlas SLV-3 as an independent vehicle. It was only discovered after Gemini 9 had rendezvoused with it that the launch had itself failed, as the payload fairing had not separated.