The idea seems simple enough. Have a sail that can capture the solar wind and use it to propel a spacecraft. This is the concept behind NASA’s Nanosail-D satellite. A joint project between NASA’s Ames Research Center and NASA’s Marshall Space Flight Center, Nanosail-D was launched in November 2010 as a sub-satellite riding on another NASA research satellite called FASTSAT. The mission was at first thought to be lost when the Nanosail satellite failed to eject from FASTSAT however on January 19th the satellite unexpectedly popped out of its carrier and began transmitting telemetry data. NASA quickly issued an appeal to amateur radio operators across the world to assist it in collecting data from the satellite.
The next day I got an email from a local ham and avid space enthusiast Nelson, VE8NE, looking to borrow a yagi antenna and a UHF handheld radio to try to receive the signal from Nanosail-D. I knew from experience that picking up the low-powered signal from a tiny microsatellite is really not something you want to attempt for the first time, outside at 35 below zero, and in the dark, so I invited Nelson to come over in the evening and we’d use my satellite station to receive the data.
Now all this wasn’t really news to me. I’d seen the request from NASA in passing but it didn’t strike me as anything unusual. The use of amateur radio frequencies on tiny research satellites is not uncommon and neither is asking the amateur radio community for assistance to downlink the telemetry. It’s usually a rather ho-hum kind of deal but as I looked into this one I realized that it was actually going to do something exciting. Exactly three days after being released from the "mother-ship" the satellite was programmed to automatically unfurl a gigantic solar sail and that 72-hour timer was due to run out tonight! A quick check of the orbital parameters showed that the satellite would pass by several times and, shortly after the sail was set to deploy, it would pass almost directly overhead. Looking at the ground track I also realized that the satellite would be flying over mostly open ocean on that particular orbit and we might even be one of the first stations to confirm the sail deployment. Needless to say, I got more interested in a hurry!
I dug up the data format for the telemetry frames and hacked up a quick Excel spreadsheet to decode the data so we could tell what was happening. Shortly before the first pass Nelson arrived and we got everything set up. My entire station is automated so once the satellite came over the horizon all I had to do was push a button. The exact position of the satellite is computed mathematically based on the current orbital elements, our precise location on the earth, and the exact time. The tracking software calculates the antenna pointing angles and passes that data to my antenna control program. It also figures out how much to adjust the receiver frequency to compensate for the Doppler shift as the satellite approaches and passes that information along to the radio control program. Finally, the signal from the radio is fed back into the computer sound card where another program turns the received audio back into digital data and displays it on the screen.
The first pass was a bit of a disappointment. The signal was much weaker than I had anticipated and all we decoded were a few partial data packets. As the satellite disappeared over the North Pole and passed over Europe we watched the Twitter feed coming from mission control at Santa Clara University in San Francisco to see if there was any news. A ham in the Netherlands had stayed up late to help relay data (it was the middle of the night there) but the last bits he was able to capture were still a few minutes before the sail was supposed to deploy. Nanosail-D slid down the far side of the world and headed over Antarctica as mission control pleaded on Twitter for someone to send them the data that would confirm whether their experiment had worked or not. Anyone in Australia or New Zealand? What about Hawaii? Alaska? Anyone..?
While we were waiting I had re-calibrated the antennas and moments after the computer said the satellite was back in range we could hear the signals from space. Nelson climbed up on the roof of the shack to see if the satellite (now supposedly sporting a 110 square foot solar sail) was visible to the naked eye while I stayed down below and tweaked the digital filters as the signals got stronger. Finally, after numerous partial decodes, a complete telemetry frame appeared on the screen followed 10 seconds later by another. I quickly pasted the data into my spreadsheet and there it was: SAIL DEPLOYED!
Screen shot of the decoded telemetry. The sail deployed right on schedule!
I hollered to Nelson (still up on the roof) that we got it and immediately transferred one of the frames to NASA with the comment "Merry Christmas!" in the notes field. After Nelson announced on Twitter that we got the confirmation of sail deploy, the guys at mission control asked us (via Twitter) to also send the data to them by email. Shortly after that here is what they posted:
@NanosailD I have data from @naeisel and am checking. First look is promising. Sorry that I have to verify and confirm. Will let everyone know soon.
@NanosailD John @naeisel has done it! I have two valid data sets and both have the correct signatures.
@NanosailD NanoSail-D has sent data that it deployed the sail. Will wait until tomorrow morning for ground based tracking to confirm.
I got a nice email from NASA the next morning confirming that our data was good and we were the first station to report the indications they had been looking for. Never a dull moment in this hobby!
73
John - VE8EV
The automatic confirmation page received after submitting telemetry.
