UC Berkeley's Space Sciences Laboratory (SSL) currently operates a fleet of seven NASA satellites, which conduct research in the fields of space physics and astronomy. The newest addition to this fleet is a high-energy X-ray telescope called the Nuclear Spectroscopic Telescope Array (NuSTAR). Since 2012, SSL has conducted on-orbit operations for NuSTAR on behalf of the lead institution, principle investigator, and Science Operations Center at the California Institute of Technology. NuSTAR operations benefit from a truly multi-mission ground system architecture design focused on automation and autonomy that has been honed by over a decade of continual improvement and ground network expansion. This architecture has made flight operations possible with nominal 40 hours per week staffing, while not compromising mission safety. The remote NuSTAR Science Operation Center (SOC) and Mission Operations Center (MOC) are joined by a two-way electronic interface that allows the SOC to submit automatically validated telescope pointing requests, and also to receive raw data products that are automatically produced after downlink. Command loads are built and uploaded weekly, and a web-based timeline allows both the SOC and MOC to monitor the state of currently scheduled spacecraft activities. Network routing and the command and control system are fully automated by MOC's central scheduling system. A closed-loop data accounting system automatically detects and retransmits data gaps. All passes are monitored by two independent paging systems, which alert staff of pass support problems or anomalous telemetry. NuSTAR mission operations now require less than one attended pass support per workday.
The Mission Operations Group at UC Berkeley's Space Sciences Laboratory operates a highly automated ground station
and presently a fleet of seven satellites, each with its own associated command and control console. However, the
requirement for prompt anomaly detection and resolution is shared commonly between the ground segment and all
spacecraft. The efficient, low-cost operation and "lights-out" staffing of the Mission Operations Group requires that
controllers and engineers be notified of spacecraft and ground system problems around the clock. The Berkeley
Emergency Anomaly and Response System (BEARS) is an in-house developed web- and paging-based software system
that meets this need.
BEARS was developed as a replacement for an existing emergency reporting software system that was too closedsource,
platform-specific, expensive, and antiquated to expand or maintain. To avoid these limitations, the new system
design leverages cross-platform, open-source software products such as MySQL, PHP, and Qt. Anomaly notifications
and responses make use of the two-way paging capabilities of modern smart phones.
Since its launch in 1999, the Far Ultraviolet Spectroscopic Explorer (FUSE) has had a profound impact on many areas of astrophysics. Although the prime scientific instrument continues to perform well, numerous hardware failures on the attitude control system, particularly those of gyroscopes and reaction wheels, have made science operations a challenge. As each new obstacle has appeared, it has been overcome, although sometimes with changes in sky coverage capability or modifications to pointing performance. The CalFUSE data pipeline has also undergone major changes to correct for a variety of instrumental effects, and to prepare for the final archiving of the data. We describe the current state of the FUSE satellite and the challenges of operating it with only one reaction wheel and discuss the current performance of the mission and the quality of the science data.
The Far Ultraviolet Spectroscopic Explorer is a NASA Origins mission
launched in June 1999 to obtain high-resolution spectra of astronomical sources at far-ultraviolet wavelengths. The science objectives require the satellite to provide inertial pointing at arbitrary positions on the sky with sub-arcsecond accuracy and stability. The requirements were met using a combination of ring-laser gyroscopes, three-axis magnetometers, and a fine error sensor for attitude knowledge, and reaction wheels for attitude control. Magnetic torquer bars are used for momentum management of the reaction wheels, and coarse sun sensors for safe mode pointing.
The gyroscopes are packaged as two coaligned inertial reference units of three orthogonal gyroscopes each. There are four reaction wheels: three oriented along orthogonal axes, the fourth skewed at equal angles (54.7°) with respect to the others. Early in the mission the gyroscopes began showing signs of aging more rapidly than expected, and one failed after two years of operation. In addition, two of the orthogonal wheels failed in late 2001. The flight software has been modified to employ the torquer bars in
conjunction with the two remaining wheels to provide fine pointing control. Additional new flight software is under development to provide attitude control if both gyroscopes fail on one or more axes.
Simulations indicate that the pointing requirements will still be met, though with some decrease in observing efficiency. We will describe the new attitude control system, compare performance characteristics before and after the reaction wheel failures, and
present predicted performance without gyroscopes.
The Far Ultraviolet Spectroscopic Explorer (FUSE) satellite was launched into orbit on June 24, 1999. FUSE is now making high resolution ((lambda) /(Delta) (lambda) equals 20,000 - 25,000) observations of solar system, galactic, and extragalactic targets in the far ultraviolet wavelength region (905 - 1187 angstroms). Its high effective area, low background, and planned three year life allow observations of objects which have been too faint for previous high resolution instruments in this wavelength range. In this paper, we describe the on- orbit performance of the FUSE satellite during its first nine months of operation, including measurements of sensitivity and resolution.
There are now a large number of space-based observatories as well as several queue-scheduled ground-based observatories. As each new telescope is brought on line, astronomers find more ways to increase their scientific return through multi- wavelength campaigns between the available telescopes. Observers can and should be involved in the coordination process from the beginning. They need to be informed about the issues, understand their true requirements and stay in touch with the involved observatories, but this is not always sufficient. Starting in 1995 the schedulers for five telescopes began contacting each other directly to plan campaigns in a way that truly met the goals of the observers. This was very beneficial because observatories have different scheduling constraints and sometimes different names of the same constraints, as well as different proposal cycles. Because the number of tightly coupled observations in increasing, it would make sense to investigate automating the comparison of viewing opportunities. Innovations in observatory coordination include trading telescope time (as Chandra and HST have) so that one observatory can award coordinated time between two telescopes. The process of coordinating observations will be discussed along with feedback from successful observers and advice to the potential observer.
The Extreme UV Explorer satellite (EUVE) was launched on June 7, 1992 with seven microchannel plate detectors behind four telescopes. All seven detectors have been operating continuously since then, cycling the high voltage bias to half voltage during the daylight portions of the orbit as well as during passage through the South Atlantic Anomaly. This paper will present the time history of the detector performance characteristics, including spatial and spectral response, gain, and flat fields. We will also discuss our experiences with the thin-film filters used to define the detector EUV bandpasses including spatial and spectral response, gain, and flat fields. We will also discuss our experiences with the thin-film filters used to define the detector EUV bandpasses including the development of 'micro' pinholes in the Al/Ti/C filters. We then illustrate specific examples of detector problems and their solutions, such as 'dithering' the spacecraft pointing to average out the small scale image distortions and off-axis pointing to avoid an on-axis 'deadspot'.