What does "product end of life" mean to you?
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"Goodbye, Mr. Smith" - SuitSat-1 is
released!
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Well, if you're an
astronaut in the
International Space Station
(
ISS), and you've got an out of date spacesuit, it's an
opportunity to have a little fun.
Unlike some systems, equipment used on the Space Station isn't left around
until failure - especially something as life-critical as a spacesuit. So,
engineers at NASA got together with Applications Engineers at Microchip and
SuitSat-1 was born.
Yes, SuitSat-1. On February 3 2006, NASA, in cooperation with Microchip
Technology, pushed an end-of-life Orlan spacesuit out the pod bay door...
uh, I mean the ISS airlock - and let it gently float in Earth's orbit. But
first, they added a few cool attachments.
See, a year before the launch of SuitSat-1, Steve Bible, an Applications
Engineer at Microchip Technology, got a call from his old friend and retired
NASA engineer Lou McFidan. Lou explained to Steve that a Russian Orlan
spacesuit on the ISS had reached it's operational end-of-life in Feb 2004, and
the fellas at NASA were throwing around a few ideas about what they could do to
have some fun with the spacesuit. One of the ideas being seriously considered
was just throwing the suit out - out of an airlock - with a radio and some
sensors to record items like the suit's temperature, the battery voltage, and
the mission elapsed time. It was agreed that some sort of embedded systems board
would be needed to manage and control the data.
And so, when Lou at NASA asked his friend Steve at Microchip, "Can a PIC
microcontroller be used for this application?", Steve replied with a resounding,
"Yes!".
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| l. to r: Steve Bible, SuitSat-1, Joe Julicher |
Steve recruited another Microchip veteran, Principle
Applications Engineer Joe Julicher, to assist in the development of the SuitSat
controller board. The controller board uses a Microchip PIC18F8722
microcontroller, MCP9800 temperature sensor, and MCP6022 opamps. Voice
messages from children around the world were digitized and placed in the
microcontroller's Flash memory, and the sounds transmitted over amateur
radio. The controller also calls out telemetry using a
digitized voice encoded in ADPCM that voices the suit's temperature,
battery voltage, and mission elapsed time. The PIC18's ECCPWM timer module is
responsible for synthesizing the encoded data into audio, which is then fed to
the radio. Students all over the world can listen to these greetings from space
using a simple amateur FM radio tuned to 145.990 MHz.
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While Steve and Joe could not radiation harden the
electronics, they did test the controller board in it's die cast aluminum box
down to a chilling -40°C. As you will see in the photo, all the electronics fit
inside the Suit with a switch box and antenna fitted to the helmet (at no time
was the phrase "Borg implants" used). Exposed to the fierce rays of the sun, the
suit's environmental controls are turned off to conserve battery power.
The controller PCB and switch box were designed and assembled at
Microchip. The radio and antenna was designed and developed by volunteers
in Florida. The complete SuitSat Flight integration was
completed at Microchip's laboratory in Arizona in June. Two complete
flight units were delivered to NASA in Houston Texas, USA and then were
shipped to Russia. There it underwent certification testing and final
flight integration.
As one astronaut cheerfully called out, "Good-bye, Mister Smith",
SuitSat-1 was placed into orbit on Feb 3, 2006 at
5:02PM U.S. Central Time.
SuitSat transmits for 30 seconds, pauses for 30 seconds, and
then repeats. "This is SuitSat-1, RS0RS" the transmission begins,
followed by prerecorded greetings in five languages. The greeting contains
"special words" in English, French, Japanese, Russian, German and Spanish for
students to record and decipher. Awards will be given to students who
successfully decipher the message.
The next message details SuitSat's telemetry data: temperature, battery power
and mission elapsed time. The transmission ends with a slow scan television
picture.
The lifespan for the suit's three batteries was estimated to be at least
three days. The orbit is expected to decay after 3-6 weeks after which the suit
should safely burn up in the atmosphere.
(editor's note: while SuitSat's three batteries were expected to be good for
three days from it's Feb 3rd launch, at the time of this article SuitSat is
still dutifully transmitting it's signal)
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