ARLA/CLUSTER: Universidade de Cornell solicita a colaboração dos radioamadores.

[João Gonçalves Costa]

Cornell University chip satellite team invites Ham Radio collaboration

A group of Cornell University-developed, fingernail-sized satellites may travel to Saturn within the next decade, and as they flutter down through its atmosphere, they will collect data about chemistry, radiation and particle impacts.

Three prototypes of these chip satellites, named "Sprite," were mounted on the International Space Station during a recent spacewalk. The thin, 1-inch-square chips are mounted to the external Materials International Space Station Experiment (MISSE-8) pallet, exposing them to the harsh conditions of space to see how they hold up and transmit
data.

Zac Manchester at Cornell University explained that the chips transmit as beacons with 10 milliwatts of RF power at 902 MHz using MSK modulation (minimum-shift keying) with a chipping rate of 50 kbps. The Cornell team invites AMSAT satellite operators to collaborate with this experiment to determine conditions in which the low-power signal has 
been detected on the ground.

The Cornell ground station consists of a 18 dBi yagi with a GNU Radio and USRP receiver (http://www.ettus.com/products). A significant challenge is that the MISSE-8 pallet the chips are on is mounted on
the anti-nadir side of the space station, facing away from the earth. The team is hoping to be lucky to catch some kind of reflection off the ISS structure.

Beyond being able to detect the signal on Earth, decoding the message requires signal processing. The chips all transmit on the same frequency, each with it's own PRN code. The Cornell team uses these codes to differentiate each one, as well as to provide signal processing gain. At Cornell, data is being recorded and post-processed with 
a standard PC.

To track these chip satellites just use the ISS keplerian elements because they are mounted on the space station.

Mason Peck, Associate Professor Mechanical and Aerospace Engineering at Cornell University wrote, "Receiving the full sequence of data per se is not of interest, but the mere reception of it (a single digital bit, for us), indicates successful transmission. If you would like to serve as one of the lucky few to try detecting this signal, please follow up with Zac Manchester (zrm3  cornell.edu). We definitely welcome the collaboration of HAM operators."

More information be found at these sources:
http://tinyurl.com/3fs5ks7 (spacemart.com)
http://www.spacecraftresearch.com/blog