OFFEQ – 2 Orbit and Attitude Flight Evaluation Report

Offeq-2, Israel's second research and development satellite, was inserted into an orbit of 214 km perigee altitude by 1570 km apogee altitude on April 3, 1990. Its primary mission was to further demonstrate IAI's satellite technology development and its ground station's ability to track the satellite, send it commands and receive its telemetry. The Offeq-2 satellite was expected to be on-orbit for about two to two and a half months (60 to 75 days), and actually was on orbit over three months (97 days). It was expected, due to the dynamic behavior of a spin stabilized satellite under the influence of drag and orbital regression, to enter a period of electrical power loss. This was also expected on Offeq-1 but did not occur due to the rapid development of the coning angle. However, this did occur on Offeq-2, on May the 2nd, as predicted, due to the lack of this rapid coning development. Power did return on May the 8th, and we were able to reconstruct this event successfully. During the lifetime of Offeq-2, all its objectives were accomplished. The TLM data received provided very valuable information for future use in the planning, designing and operating Israel's future satellites. This paper reports on the integration of subsystem telemetry data evaluation into a multiple reconstruction of the satellite's performance over several events. This was accomplished using a systems engineering approach, which combined the efforts in several areas: attitude determination via sensor TLM data, dynamic simulations of the attitude and orientation motion, orbital semi-major axis decay, coning angle estimation and electrical power TLM analysis and reconstruction, including analysis of the thermal TLM. We were able to successfully reconstruct the events of the flight including the power outage and resumption.