On March 9th 2009, the STPSat-1 satellite celebrated its second year of successful on-orbit operations. The spacecraft was launched in 2007 on board an Atlas-V rocket as part of the STP-1 mission. Tiger Innovations designed the Integrated Electronics Module which provides all C&DH and EPS functions for STPSat-1. Additionally, we provided the spacecraft EGSE and engineering support services to the mission. STPSat-1 continues to operate exceptionally on orbit, producing valuable data for the NRL scientists well past its design life.
The United States Air Force transferred spacecraft control authority for the STPSat-1 Spacecraft to the Naval Research Lab on 1 June 2008. The USAF had been operating the vehicle since its launch in 2007 through its designed mission life of 13 months. Under contract with the NRL, Tiger Innovations is providing its StreamLINK Ground Control System (SGCS) and engineering support to autonomously operate STPSat-1 during the mission extension period.
The StreamLINK system was deployed to support the life extension mission and includes a flight operations version of our Integrated Test Rack (ITR). The SGCS consists of the Tiger Innovations Frame Sync/Command Formatter, and automated operations package that allows 24/7 “lights out” operations. The SGCS utilizes the same StreamLINK backend that was used during integration and test of the vehicle, which allowed us to field a working ground system in less than 2 weeks. It is currently integrated with the Blossom Point Tracking Facility, which provides the RF interface, automated antenna operations, and engineering support during the operational phase of the mission. In addition to providing the StreamLINK system, Tiger Innovations has developed scripts to autonomously take passes, record data, upload commands, and generate email and phone alerts in the event of an anomaly. The first 9 months of the mission extension have gone very well, with no SC failures and a relatively smooth transition from 24/7 ops to a fully automated ground station.
The primary experiment, SHIMMER, has now measured the PMC diurnal variation for the two northern seasons of 2007 and 2008, and surprisingly, the variation is quite different. Even though a semidiurnal signature, that is two peaks per day — one in early morning and one in the late afternoon — was observed in 2007; in 2008, the variation was diurnal or one peak per day. This result has important implications for the inference of long-term trends from historical, space-based PMC observations because NASA and NOAA satellites that have observed PMCs over the last 25 years have all been launched into sun-synchronous orbits with different, fixed local times. Until the diurnal variation of these clouds is better understood, the SHIMMER data show that it is premature to make firm conclusions about multi-decadal trends in PMCs.
STPSat-1 was built by AeroAstro Inc. for the USAF Space Test Program. The primary experiment, Spatial Heterodyne Imager for Mesospheric Radicals (SHIMMER), is a high-resolution ultraviolet spectrometer based on the optical technique known as Spatial Heterodyne Spectroscopy (SHS). SHS facilitates the design of low mass, low power, high throughput spectrometers for space-based remote sensing. The secondary experiment, the Computerized Ionospheric Tomography Receiver in Space (CITRIS), will investigate irregularities that affect propagation of satellite-to-ground links for GPS and communications. STPSat-1 has successfully completed its 13 month design mission and is currently under control of the Naval Research Lab in support of a mission extension effort.