Tuesday, April 13, 2010

Nanosats -- Specks in Space

Sputnik I
In 1957, Russia launched Sputnik I, a beachball-sized device that weighed in at 183.9 pounds and struggled to carry a thermometer and two radio transmitters that functioned for just 21 days. Times passed. Boosters built enough muscle by 2005 to put iPSTAR-1 into orbit -- a 14,341-pound monster that will provide Internet access and broadband services to businesses and consumers around the world for an indefinite period of time. But the next chapter in the satellite story will be  about nanosats, devices with a mass between 2.2 and 22 pounds and vast potential in communications and recon applications -- from humanitarian to military. (There are even picosatellites in the offing, weighing as little as 0.22 pounds.)


Nanosats like the SMDC-ONE weigh less than 10 pounds and are about 4x4x13 inches in size. Developed by the U.S. Army Space and Missile Defense Command and the Army Forces Strategic Command, SMDC nanosats are inexpensive by satellite standards, costing about $1 million each, and expected to be much less as manufacturing processes are refined. The first SMDC nanosat went into orbit in 2009.

Engineers foresee nanosats functioning in swarms -- clouds of devices that will work together in varieties of configurations to accomplish ever-changing missions. Some swarms will answer to a larger mother satellite to communicate with each other and with ground controllers.

James Cutler, an assistant professor in the Department of Aerospace Engineering at the University of Michigan, is working with SRI International, one of the world's largest contract research institutes, to develop nanosatellites such as the Radio Aurora Explorer (RAX), a craft funded by the National Science Foundation to study space weather. RAX, a Cubesat device weighing 6.6 pounds, is scheduled for a launch in May 2010.

A team of engineering students working under Cutler is designing a deployable high-gain UHF antenna for nanosatellites. They’ll  integrate the antenna into an eXtendable Solar Array System (XSAS) that’s currently in development. Typical nanosatellite antennas have low-gain (2-5dBi) as a consequence of size constraints. In order to use a nanosaatellite for tracking or remote data collection applications, such as tracking animal migration, pipeline sensor data collection and emergency beacon communication, the nanosat requires a higher gain antenna. The student team’s goal is to design an antenna with 11dBi gain that will be deployed with the XSAS system. They explain their project in the following video.

Nanosatellites will also be a tool to help keep space clean. Fifty years of abandoning spacecraft in orbit has left about 5,500 tons of debris cluttering space around the planet and posing a substantial threat to hugely expensive unmanned and manned spacecraft. If current practices prevail, engineers expect that number to grow at a rate of five percent a year. Although nanosats won't cut the amount of debris already whizzing overhead, they will help stop future missions from adding to the problem.


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The problem is that junk that is already there is generating new debris via impacts. According to NASA, we have already reached the runaway generation of new debris, and even if stopped launching new satellites entirely, we could not stop it. There is no way to clean up the debris that is there: the stuff that is the greatest concern (< 10 cm) is to small to see and track, and there is now way you can go up and match orbits with the 100,000's of pieces that are already there in order to retrieve them (even if we could see them).

LMR-400 said...

Smaller satellites using higher gain antennas connecting at microwave frequencies are a viable option to the larger and more fragile antenna arrays.

Term Life Insurance said...

Hail to the mother satellite! I love the visual concept of the nanosats working in a cluster. A cloud of sats. Puts a whole new spin on clouds.