Free flyers can be either dedicated satellites or carriers to which the instrument mounts, which in turn interface with the Orbiter. While the capacity of the Space Shuttle is in excess of 32000 pounds, secondary payloads generally do not exceed 8000 pounds. Instrument size, shape, and mass are driven by the capabilities of the carrier within the constraints of the Shuttle and the other manifested payloads. Orbits The Shuttle can carry payloads into orbits with an inclination ranging from 28.5 degrees to 57 degrees. Altitudes at which free flyers can be deployed depend on a variety of factors but can vary from 110 nmi to over 300 nmi.
Free flyers can carry orbit adjust systems to modify orbit parameters.
Mission designs can include deployment and retrieval on the same Shuttle mission, deployment on one mission and retrieval by a later mission , or deployment and no retrieval. Attached payloads and spacecraft that are deployed and retrieved on the same mission are generally constrained to two weeks or less. Spacecraft not retrieved on the same mission as deployment can have durations from months to years. Specific environments are available from spacecraft and carrier providers. In many cases these specifications are conservative and can be relaxed by mission specific analysis.