STPSat-2/STP-SIV

The Space Test Program Standard Interface Vehicle (STP-SIV) program reduces mission cost and lead time with a common spacecraft bus, a standard payload interface accommodating up to four separate payloads or modules, and a streamlined acquisition process using an IDIQ contract. Each vehicle is designed to operate over a wide range of LEO orbits and to be compatible with a large variety of launch vehicles, including as an EELV Secondary Payload Adaptor (ESPA) rideshare. Comtech AeroAstro’s role was to design, build, and integrate the SIV bus under subcontract to prime integrator Ball Aerospace. The first SIV bus, for the STPSat-2 mission, was delivered to Ball in December 2008 for payload integration and was launched on a Minotaur IV from Kodiak, Alaska in 2010.

The STP-SIV bus design incorporates a separable Payload Standard Interface Module that may be integrated in parallel with the bus to support accelerated launch schedules and reduce technical risk. The vehicle accommodates a variety of payload configurations in low earth orbits from 400–850 km. The spacecraft also supports, without design change, a wide range of inclinations with a minimum one-year lifetime. SIV features include high mass and power margins, flight-proven heritage components, and a highly integrated mechanical and thermal design. It incorporates a flexible zero-momentum attitude control system, fixed and articulated solar arrays, integrated C&DH and power avionics, and a high-reliability SGLS transponder. Comtech AeroAstro used the Astro 200 bus as the design baseline for SIV; with most non-recurring costs retired, the Astro 200 is now available at competitive cost and with accelerated lead time. We also offer the Astro 200AS, for missions and customers desiring enhanced attitude control, stability and agility, and X-band downlink performance.

The STP-SIV program supports the Space Test Program’s goals to maximize space flight opportunities for Space Experiment Review Board (SERB) experiments. The STP-SIV bus design evolved from Comtech AeroAstro’s experience as the prime contractor for STPSat-1, launched aboard the first ESPA (Atlas-V/STP-1) in March 2007. Comtech AeroAstro both simplified and enhanced the STPSat-1 design for the STP-SIV program to improve reliability, enhance mission flexibility and orbit range, and provide the standard payload interface that is critical to supporting the maximum possible number of experiments. We also developed high fidelity development and test plans, complete operating procedures including the bus content for the Payload User’s Guide, and a detailed cost baseline enabling this bus design to be reproducible for a diverse set of mission options.