* Astronomy

three orbiting micro-satellites known as Space Technology 5 have completed their planned 90-day mission. The mission team is shutting down the spacecraft to conclude operations on Friday, June 30.

The mission primarily focused on flight testing miniaturized satellites in the harsh environment of space and evaluating their ability to make research-quality scientific measurements.
The satellites were launched on March 22. Each fully fuelled satellite weighed approximately 55 pounds when launched and is about the size of a 13-inch television.

A major milestone of the mission was reached when the spacecraft assumed a constellation formation on May 24. The satellites lined up in nearly identical orbits, like three pearls on a necklace, approximately 220 miles apart. Reaching formation required seven manoeuvres using miniaturized micro-thrusters. Each spacecraft has a single micro-thruster the size of a quarter to perform both attitude- and orbit-adjustment manoeuvres.
The mission demonstrated the benefits of using a constellation of spacecraft to perform scientific studies of the beautiful auroral displays that occur near Earth's polar regions. The spacecraft simultaneously traversed electric current sheets and measured the magnetic field using miniature magnetometers.

"Taking measurements at the same time in different locations allowed scientists to better estimate the thickness of current sheets and how they vary over time. This could not have been done with a single spacecraft, no matter how capable." - Guan Le, mission project scientist at NASA's Goddard Space Flight Centre, Greenbelt, Md.

The mission validation team demonstrated the sensitivity of miniature magnetometers, and suitability of the satellites for supporting scientific measurements. Over the next few months, the team will process the mission's magnetometer data, complete its assessments of the performance of the satellite constellation and report initial findings.

The mission also demonstrated an innovative communications technology. The satellites used miniature spacecraft radio transponders for space-to-ground communications and tracking. The transponders were coupled with conventional and computer-optimised or -evolved antennas. The transponders and antennas performed flawlessly.

The satellites' miniature power system demonstrated a high level of performance. All spacecraft lithium ion batteries stayed above 90 percent charge, even during some tests intentionally designed to use them. The high-efficiency solar arrays on all three spacecraft produced more power than predicted prior to launch, and their batteries performed to expectations.

During the final days of the mission, the emphasis was on demonstrating ground system technologies. The ground system is highly automated to reduce the cost of operating multiple spacecraft as a single constellation rather than operating them individually. This type of ground system will help pave the way for an affordable means of simultaneously flying from 10 to hundreds of micro-satellites.

The project was developed and tested at Goddard. It is part of the New Millennium Program, which develops and tests high-payoff technologies that provide future science mission capabilities with reduced cost and risk. Each flight acts as a test track for competitively-selected technologies, mission objectives and operations concepts. New Millennium is managed for NASA by the agency's Jet Propulsion Laboratory, Pasadena, California, US.

Source NASA