A Deployment Strategy for Multiple Secondary Payloads on the MLV-05 Mission

The Department of Defense (DoD) Space Test Program (STP) provides space flight for qualified DoD sponsored experiments at no charge to the experimenter, via the DoD-Space Experiments Review Board (DoD-SERB). Through the Air Force Space Command, STP is supplied with a Medium Class Launch Vehicle approximately every 4 years for SERB payloads. The next launch will be on a Delta IV-Medium in the fiscal year 2006. Originally scheduled for 2005 the mission has been temporarily named "MLV-05". STP has initiated mission design activities and has defined a baseline mission. The current baseline is for an Eastern Range launch to low earth orbit (LEO). Five (possibly six) separate spacecraft will be deployed from an EELV Secondary Payload Adapter (ESPA) ring after which the launch vehicle’s upper stage will take the primary payload to a geosynchronous transfer orbit (GTO). This paper discusses the development of a deployment strategy for the MLV-05 secondary payloads subject to the payloads’ requirements, the constraints of the separation system, and the timeline for the primary payload’s orbit maneuver. The objective is to deploy the secondary payloads in a manner that limits the possibility of close approaches among these payloads and the upper stage following their separation. Because of differing ballistic coefficients the satellites will eventually fall into a natural order in the along track direction. This order dictates the sequence in which they are deployed. The uncertainty in the deployment springs determines the minimum safe difference in the deployment velocities. Three of the satellites in the current baseline mission will form the TechSat 21 formation flying experiment. Physical constraints require the three TechSats to occupy alternating locations on the ESPA ring. Each TechSat can be paired with the satellite opposite it on the ring and the timeline for the deployment can be reduced by deploying each pair together, but in opposite directions. The strategy takes into consideration the desire of the TechSats to establish their formation several days after deployment. Should one of the TechSats fail to deploy its solar array the difference in deployment velocities allows adequate time for the others to perform collision avoidance maneuvers, if needed.