Diane C. Roussel-Dupre

On-Orbit Flight Results from the Reconfigurable Cibola Flight Experiment Satellite (CFESat)

The Cibola Flight Experiment (CFE) is an experimental small satellite developed at the Los Alamos National Laboratory to demonstrate the feasibility of using FPGA-based reconfigurable computing for sensor processing in a space environment. The CFE satellite was launched on March 8, 2007 in low-earth orbit and has operated extremely well since its deployment. The nine Xilinx Virtex FPGAs used in the payload have been used for several high-throughput sensor processing applications and for single-event upset (SEU) monitoring and mitigation. This paper will describe the CFE system and summarize its operational results. In addition, this paper will describe the results from several SEU detection circuits that were performed on the spacecraft.

The Cibola Flight Experiment

Over the past 15 years many organizations have researched the use of Static-Random Access Memory (SRAM)-based Field-Programmable Gate Arrays (FPGAs) in space. Although the components can provide a performance improvement over radiation-hardened processing components, random soft errors can occur from the naturally occurring space radiation environment. Many organizations have been developing methods for characterizing, emulating, and simulating radiation-induced events; mitigating and removing radiation-induced computational errors; and designing fault-tolerant reconfigurable spacecraft. Los Alamos National Laboratory has fielded one of the longest space-based FPGAs experiments, called the Cibola Flight Experiment (CFE), using Xilinx Virtex FPGAs. CFE has successfully deployed commercial SRAM FPGAs into a low-Earth orbit with Single-Event Upset (SEU) mitigation and was able to exploit effectively the reconfigurability and customization of FPGAs in a harsh radiation environment. Although older than current state-of-the-art FPGAs, these same concepts are used to deploy newer FPGA-based space systems since the launch of the CFE satellite and will continue to be useful for newer systems. In this article, we present how the system was designed to be fault tolerant, prelaunch predictions of expected on-orbit behaviors, and on-orbit results.

MTI science, data products and ground data processing overview

The mission of the Multispectral Thermal Imager (MTI) satellite is to demonstrate the efficacy of highly accurate multispectral imaging for passive characterization of urban and industrial areas, as well as sites of environmental interest. The satellite makes top-of-atmosphere radiance measurements that are subsequently processed into estimates of surface properties such as vegetation health, temperatures, material composition and others. The MTI satellite also provides simultaneous data for atmospheric characterization at high spatial resolution. To utilize these data the MTI science program has several coordinated components, including modeling, comprehensive ground-truth measurements, image acquisition planning, data processing and data interpretation and analysis. Algorithms have been developed to retrieve a multitude of physical quantities and these algorithms are integrated in a processing pipeline architecture that emphasizes automation, flexibility and programmability. In addition, the MTI science team has produced detailed site, system and atmospheric models to aid in system design and data analysis. This paper provides an overview of the MTI research objectives, data products and ground data processing.

ALEXIS small satellite project: initial flight results

We report the launch and rescue of the ALEXIS small satellite. ALEXIS is a 113-kg satellite that carries an ultrasoft x-ray telescope array and a high-speed VHF receiver/digitizer (BLACKBEARD), supported by a miniature spacecraft bus. It was launched by a Pegasus booster on 1993 April 25, but a solar paddle was damaged during powered flight. Initial attempts to contact ALEXIS were unsuccessful. The satellite finally responded in June, and was soon brought under control. Because the magnetometer had failed, the rescue required the development of new attitude control techniques. The telemetry system has performed nominally. The BLACKBEARD experiment was turned on shortly after contact, and has returned its first data. We discuss preliminary lessons learned from ALEXIS.

The anomalous background observed by the ALEXIS telescopes

The ALEXIS satellite, launched 25 April, 1993 by the Pegasus Air Launched Vehicle, is in a 750×850 km, 70 degree inclination orbit. The six on board telescopes tuned between 66–93 eV were designed to eliminate the geocoronal background either with the He II 304 A anti‐reflection coating on the mirror or filters in front of the detector. Before launch, the telescopes were assumed to be continuously operated with an estimated background counting rate of 10–30 c/s. At first light, it was these assumptions that were proven to be incorrect. This paper presents the results of the study of the anomalous background observed by the ALEXIS telescopes.

ALEXIS: the six-year telescope flight experience

The array of low energy x-ray imaging sensors (ALEXIS) satellite was launched from the 4th flight of the Pegasus booster on 25 April 1993 into an 800 km, 70 degree inclination orbit. After an initial launch difficulty, the satellite was successfully recovered and is still producing 100 MB of mission data per day. ALEXIS, still going strong in its sixth year, was originally designed to be a high risk, single string, Smaller-Faster-Cheaper satellite, with a 1-year nominal and a 3-year design limit. This paper will discuss the on-orbit detector performance including microchannel plate operation, pre- and post-flight calibration efforts, observed backgrounds and impacts of flying in a high radiation environment.

A remote sensing lab in space

Cibola Flight Experiment is a small experimental satellite that hosts a reconfigurable computer payload. The configurable high speed processing unit has the power to do significant data compression and the flexibility to run a wide variety of applications. The reconfigurable computer is made up of networks of radiation tolerant SRAM-based Field Programmable Gate Arrays (FPGAs). The ability to reconfigure provides the flexibility to do a lot of things not usually possible in a space environment. Payload algorithm development continued while the spacecraft was being integrated for launch rather than being frozen months in advance. A library of applications resides on the spacecraft, making theater-specific payload configuration possible. Applications are in an on-going state of development and improvements. This has allowed the project to adjust to spacecraft and payload anomalies, real-world signal environments and a wide range of post-launch needs.

ALEXIS Lunar Observations

The ALEXIS small satellite was designed as a large area monitor operating at extreme ultraviolet wavelengths (130 – 190 A). At these energies, the moon is the brightest object in the night sky and was the first source identified in the ALEXIS data. Due to the design of ALEXIS and the lunar orbit, the moon is observed for two weeks of every month. Since lunar emissions in the extreme ultraviolet are primarily reflected solar radiation these observations may be useful as a solar monitor in the extreme ultraviolet. The data show distinct temporal and spectral variations indicating similar changes in the solar spectrum. We will present a preliminary dataset of lunar observations and discussions covering the variations observed and how they relate to the solar spectrum.

The ALEXIS Point Source Detection Effort

Los Alamos National Laboratory’s A LEXIS satellite (a wide area EUV monitoring instrument) was launched April 25, 1993. Due to the damage sustained at launch by the satellite, the ALEXIS project team has had to spend over a year devising new methods to determine spacecraft attitude knowledge, essential for putting photons back on the sky correctly. These efforts have been successful and currently the ALEXIS attitude solutions are precise to better than 0.5 degree close to the original 0.25 degree pre-flight specification. This paper will discuss the number and types of point sources that have been revealed in the ALEXIS data, to date. We will also discuss ALEXIS observations of the June, 1994 super outburst of the Cataclysmic Variable VW Hyi, a program to look for simultaneous EUV emission from Gamma Ray Bursts, as well as an effort to detect EUV transients with a 12 – 24 hour response time.