TacSat-4 Mission and the Implementation of Bus Standards

This paper provides an overview of the TacSat-4 mission with a focus on the COMMx payload. It discusses the lessons-learned to date and the challenges of building a payload to fly on the prototype spacecraft Bus built to the ORS Phase III Bus standards. Each TacSat experiment tests key elements of an operational system by taking frequent tangible steps to spiral capability and receive operational feedback, while moving toward Operationally Responsive Space (ORS) acquisitions. The TacSat-4 experiment’s mission was selected by a Joint panel. Tacsat-4 has several ORS system level objective including using a prototype bus to mature spacecraft bus standards for acquisition and to fly in a “low” highly elliptical orbit, enabling a new set of ORS missions that require dwell, such as communications. TacSat-4 provides a Communications-on-the-Move and Data-Exfiltration payload. Building a TacSat that operates in a high radiation, highly elliptical orbit is quite challenging for the low cost class and short schedules that TacSats must support. The COMMx payload is currently undergoing system level environmental testing. The ORS Bus Standards flight prototype is complete and ready for integration with the payload. Space vehicle integration and test will be performed from August to October 2008 with launch scheduled for September 2009