Without any fanfare, the OTV-4 mission came to an end over the weekend, landing at Kennedy Space Center’s Shuttle Landing Facility following 718 days in orbit.:
As with the previous three Orbital Test Vehicle missions, the majority of its activities remain undisclosed. However, this time the Air Force did disclose two payloads: an experimental ion thruster built by Aerojet-Rocketdyne and a NASA payload called METIS (Materials Exposure and Technology Innovation in Space) that exposed over a hundred samples of materials, such as polymers, ceramics, and more.
The fifth OTV mission has not yet been announced.