An artist's concept of the TSX-5 satellite above Earth. Photo: Orbital Sciences

The TSX-5 space vehicle, built and integrated by Orbital Sciences Corporation, is the sixth in a series of U.S. Air Force (USAF) Space and Missile Center (SMC), Space Test Platform (STP) provided small class spacecraft missions for conducting space research and development experiments. This space vehicle is a descendant of the Space Test Experiment Platform (STEP) common spacecraft bus, whose program missions included STEP-0, STEP-1, STEP-2, STEP-3, and STEP-4. TSX-5 hosts two DoD experiments, Space Test Research Vehicle-2 (STRV-2) sponsored by the Ballistic Missile Defense Organization (BMDO), and the Compact Environmental Anomaly Sensor (CEASE) sponsored by the USAF Research Laboratory (AFRL).

The TSX-5 spacecraft orbit will be elliptical with a 410 km (221 Nmi) periapsis and 1750 km (994 Nmi) apoapsis. Orbit inclination is 69 degrees with a TBD descending node. TSX-5 will be launched in April 2000 aboard an Orbital Science Corporation Pegasus XL launch vehicle. The TSX-5 space vehicle flight configuration is shown in the figure below, TSX-5 Space Vehicle. Four major physical attributes dominate the space vehicle external configuration: the spacecraft or core module, the separation system, the STRV-2 Experiment Module (EM), and the fixed geometry solar arrays.

The spacecraft primary structure is a nominal 37.5 inch (0.95 m) point-to-point 12-sided structure which provides the required strength to carry launch and handling loads. This all aluminum structure consists of a honeycomb core plate with sheet metal panels mounted to milled longerons or stringrers. The 32.40 inch (0.82 m) long STRV-2 payload is mounted to the top of the spacecraft structure. A 38.00 inch (0.97 m) diameter marman ring and V-band separation system which attaches the space vehicle to the launch vehicle, transfers launch loads between the space vehicle and launch vehicle, and permits space vehicle separation from the launch vehicle following orbit insertion. The separation system is composed of a marman band/attach ring assembly, externally mounted pyrotechnic bolt cutters, separation springs, and electrical separation connectors. The total in-flight space vehicle weight is nominally 550 lbs (249.5 kg).

Space vehicle subsystems and payloads are designed for a six (6) month mission life with a one (1) year goal, and reliability exceeding 90%. The spacecraft subsystems include an electrical power subsystem (EPS), a command and data handling subsystem (C&DH), a communications subsystem (COMMS), and an attitude determination and control subsystem (ADACS). Subsystem electronic components and the CEASE experiment are mounted internal to the spacecraft on the -X or wake oriented Core Plate.

Technicians perform final work on the TSX-5 spacecraft. Photo: Orbital Sciences

Space Test Research Vehicle-2
The STRV-2 primary objectives include demonstration of operation of optical instruments (Medium Waveband IR, MWIR, Laser communication (LASERCOM) on a low-cost, non-precision platform, downlinking of data via Lasercom, obtaining infrared background data in selected wavelength bands at low and high altitudes, and assessing performance of candidate components in the space environment.

Additional objectives of the STRV-2 experiments Space Active Modular Materials Experiment System SAMMES, Vibration, Isolation, Suppression and Steering System VISS, All Composite Experiment Spacecraft Structure ACESS , and the Engineering Test Bed (ETB) (which includes the Meteroid & Debris Impact Monitor and the Meteorid Impact Sensor) include characterization of the space environment (radiation, micrometeoroid and debris) at altitudes relevant to Brilliant Eyes, vibration isolation and suppression, assessment of contamination transport and effects aboard a low-cost satellite, and demonstration of a modular architecture for autonomous command, control and data handling. The minimum success criteria for STRV-2 include collection of IR background data for phenomenological analysis, demonstration of laser communication downlink, demonstration of vibration isolation and suppression technology, and collecting six months data on the space environment and its effects on candidate components.

Compact Environmental Anomaly Sensor
The objective of the CEASE experiment is to develop and demonstrate on-orbit, autonomous, compact, light weight, low power instrumentation to monitor the environment around a spacecraft, and to provide alerts whenever the environment is likely to cause any of the following anomalies:

• Surface Charging
• Deep Dielectric Charging
• Single Event Upsets (SEU's)
• Radiation Dose Effects

TSX-5 is expected to be the first flight of CEASE, and thus is primarily a proof of concept flight to ensure that the instrument functions as designed. Therefore, for TSX-5, CEASE's minimum success criteria is to deliver a fully integrated and tested CEASE instrument package for rapid spacecraft integration, and obtain background data for six months on the space environment and its effects on candidate components. In addition, it is desired that CEASE collect data for as long as possible on-orbit, preferably until the end of spacecraft life.