ALEXIS

Comtech AeroAstro's first spacecraft, Array of Low Energy X-ray Imaging Sensors (ALEXIS), was built for Los Alamos National Laboratory. The satellite was launch-ready 3.5 years after concept. ALEXIS was launched in April 1993 on a Pegasus booster and operated on orbit for over twelve years, far beyond its six-month design lifetime. It surpassed all mission requirements and expectations until its final decommissioning in 2005. The ALEXIS spacecraft accommodated two payloads: 1) the soft X-ray experiment, also called ALEXIS, was a novel set of wide-angle, normal incidence telescopes, which scanned half the sky every satellite rotation; 2) BLACKBEARD, an accompanying instrument, was a broadband receiver and digitizer designed to study ionospheric propagation in the 25-175 MHz band.



The spin-stabilized spacecraft was compact and efficient—the spacecraft bus comprised only 40% of the total satellite mass (45 kg bus mass, 115 kg total mass). The bus provided 50 Watts of 28 V power to the payload while consuming only 10 Watts itself. Attitude could be determined at any instant in post-processing to ±0.25 degrees.

Payload data were recorded in a Comtech AeroAstro-supplied 96 MB spacecraft mass memory at mean rates of 10 kbits/second, with peak rates reaching in excess of 100 kbits/second. The ALEXIS system employed a "store-and-forward" architecture to pass tracking, telemetry, and control, and data between the spacecraft and a single ground station at Los Alamos. Commands were uplinked at 9600 bits/second and data were downlinked at 750 kbits/second via a steerable 2-meter dish. Comtech AeroAstro designed and built the spacecraft bus and the ground station, as well as supported the launch and ground operations activities.