Tuesday, April 12, 2011

GAGA-1: The Flight

GAGA-1 flew on Sunday, April 10, 2011 and took more than 1,800 pictures of its adventure. The flight and recovery computers worked well right up until impact and the capsule landed safely in a field to the west of Cambridge.

Thanks

Before giving details of the flight, I need to thank all the people who helped make it possible. Most importantly, Ed Moore of CUSF who helped on the day with balloon filling, expertise, a good place for coffee and a snack, and the chase. He was even the one that saw the little yellow square lying on the ground through a line of trees.

Also, very important were the radio amateurs and other enthusiasts who listened to the RTTY telemetry transmitted from the capsule and uploaded to the tracker. In particular G3VZV (and M0LEP) who followed the balloon almost to the ground enabled us to find it.

And lastly thanks to the denizens of #highaltitude for advice and encouragement, and who jumped in at the 11th hour and fixed some bad XML so that the tracker would accept the telemetry transmitted by GAGA-1.

Summary

GAGA-1 flew to 32,086m altitude and spent 2h12m in the air. The first telemetry in the air came at 09:48:54 UTC and the final telemetry was received at 12:01:09 UTC. The camera took 1,856 photographs including capturing the Thames estuary, the moon and the black sky. The complete photograph set (editing out tedious repetition) can be found here. Here's the first in flight photo showing Churchill College, Cambridge:

Here's the flight track. You can interact with it through this map. The blue markers indicate where SMS messages were sent. Two were sent on ascent (the recovery computer that sent them was programmed to go quiet at 2,000m) and one was sent close to the ground.

The final moments of the flight are here. The yellow marker shows the rough landing spot, the two blue markers show where the recovery computer sent SMS messages (the second one failed) and the yellow track is telemetry received.

The ascent took 1h40m, the descent took 32m. The maximum descent rate was 77.93 m/s when the balloon burst (since the atmosphere is thin the parachute does nothing). The final descent rates was 8.2 m/s.

Here's a shot taken very high up looking down on the Thames estuary; to the bottom right there's a U bend in the river at Greenwich. The south coast is clearly visible.

A later shot shows all of London with the Isle of Wight visible in the top right:

And just before the balloon burst GAGA-1 took this photograph of the Earth and space, the Isle of Wight and London and in the distance, France.

And more of space:
And here is a shot of our little satellite:

Things that did work

1. The flight computer worked flawlessly throughout and the signal from the 10mW transmitter was audible across the UK. It was picked up 542 km away in Northern Ireland and also in Scotland (as well as around England). A triumph for the coat hanger antenna and line-of-sight. Here's a video of the transmission being received in Northern Ireland:

2. The recovery computer followed a preset state machine. Initially it transmitted its location on early ascent, and then went into a quiet mode while above GSM access level. Once above the ballistic missile height the GPS shutdown and the built in program performed a cold reset. It successfully restarted and once below 4,000m started trying to SMS its position.

It managed to send one SMS reading T+12126: 5208.8703N 00001.9362W 785m 298.92deg 26.71kph 11sats (3810mv, -1000C, RECOVERY). The -1000C indicates a temporary error reading the built in temperature sensor. RECOVERY indicates that it knew it was landing. The altitude is 785m and it was traveling (across the ground) at 26.71 kph.

3. The camera worked and took many fantastic photographs.

4. Painting the capsule fluorescent yellow turned out to important as it was spotted on the ground from a few hundred meters and through a line of trees.

5. During the flight the recovery computer dealt with unexpected errors from the GSM module (indicating no access to the GSM network) and managed to carry on.

6. All my knots held and the rigging through the capsule walls worked. The UHF antenna was badly damaged on impact as expected. Unexpected was the fact that the capsule was upside down in the field meaning that the GPS antennas would likely have been completely shielded from the sky.

Things that didn't work

1. Both computers cut out on landing. Opening the box revealed that the two battery packs (that I had hot glued in place) had come loose, the six battery pack used for the flight computer had lost a battery when it hit the ground. The batteries were in place for the recovery computer, and it had power, but it had stopped operation.

Camera removed showing battery packs unglued. The red light is the recovery computer power LED.

2. The balloon had not shredded cleanly. More than 1kg of balloon was still attached which helps explain the faster than expected descent.

3. On examining the recovery computer log there was a final attempted SMS at 186m altitude but it never made it: 5208.8826N 00002.2388W 186m 263.86deg 23.07kph 11sats (3812mV, 12C, RECOVERY). Also noted were some unexpected errors (+CMS ERROR: 331) which the code successfully overlooked. These indicate that we were trying to SMS with no network.

4. I couldn't access the tracker using my laptop in the car because O2 Internet Tethering was blocking maps.google.com for some reason.

5. The temperature values are surprising. The minimum external temperature measured was -20C and then the temperature rose with altitude. Although this is expected in the stratosphere it should have been much colder. This may indicate that the sun was warming the external temperature sensor which was encased in a small black plastic straw. Also on descent the internal temperature dropped. I suspect that this was caused by cold air being forced into the capsule around the camera lens.

6. There are a couple of unexplained erroneous bits of telemetry corresponding to spikes in temperature and altitude at the same time (see the above chart).

7. On booting the camera it failed to turn on twice resulting in me changing the batteries and finding that it would only boot with the SD card missing. Putting the SD card back in would then work. I saw this twice.

Appendix

1. The complete log of telemetry received is log.

2. The log kept by the recovery computer is here.

3. The log kept by the camera is here.

4. The source code used for the camera and both computers is here.

The camera has three temperature sensors in it covering the lens, the electronics and the battery compartment. Here's a graph showing its temperatures. Note that the front of the lens is exposed to the air with no protection. The heating at the end seems to be because the capsule sat around on the ground in full sunlight in a lovely afternoon while I searched for it.

Here are two shots of GAGA-1 as we found it on the ground showing the balloon, parachute and capsule. Note a small number of balloon fragments are in the rigging of the parachute and a large amount is still attached to the main cord (it's not clear from the photographs but the cords were not tangled).

The capsule, upside down, baking in the sun and still taking pictures.

History

A handy complete history of the GAGA-1 project from its inception in July, 2010 to the flight itself.

July 8, 2010: GAGA-1

July 17, 2010: Some initial investigations

September 5, 2010: Camera Hacking

September 8, 2010: Redundancy and Independence

September 9, 2010: Honey, there's a camera in the freezer

September 12, 2010: 2,766 tedious photographs and a log file

September 13, 2010: Weight Budget and The Capsule

September 19, 2010: Capsule paint job

September 20, 2010: Source Code Repository

October 4, 2010: Computer Mounting

November 5, 2010: Recovery Computer

November 20, 2010: Recovery Computer Ground Test

November 27, 2010: Capsule insulation and antenna mounting

November 28, 2010: CoCom limit for GPS

December 6, 2010: The Camera Hole

January 22, 2011: Getting close to completion

January 26, 2011: Flight Computer radio's first transmission

January 27, 2011: Voltage divider calculator for Radiometrix NTX2

January 28, 2011: Calculating, rather than experimenting to find, resistor values for the NTX2 voltage divider

February 5, 2011: Voiding the warranty (for great justice!)

February 8, 2011: Batteries

February 10, 2011: Temperature Measurement

February 18, 2011: Parachute

February 19, 2011: Working flight computer and The lovely sound of RTTY

February 25, 2011: Another little freeze test

February 28, 2011: Flight computer testing

March 13, 2011: The Stack

March 24, 2011: Parachute test

March 31, 2011: Tentative launch date: April 10, 2011

April 5, 2011: Integration testing

April 8, 2011: Looking good for Sunday

April 10, 2011: Quick post-flight update

Vostok

In my original post on GAGA-1 in July, 2010 I said I hoped to launch in time for the 50th anniversary of Yuri Gagarin's Vostok 1 flight. It occurred at 0607 UTC on April 12, 1961. This post comes exactly 50 years later.

GAGA-1: The Movie

My friend Eric Melski suggested while I was working on GAGA-1 that the appropriate soundtrack for the work would be Europe's The Final Countdown.

And so, for Eric and for everyone else, here are all 979 photographs taken during the flight set to epic Swedish 1980s synth rock.

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If you enjoyed this blog post, you might enjoy my travel book for people interested in science and technology: The Geek Atlas. Signed copies of The Geek Atlas are available.

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