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Hello everyone,
I'm happy to see that you have an interest in the SPOT-controlled high atmosphere balloon project. This project will be moving very fast (in fact there is only 15 days before the closest forecasted launch date) so be sure to read your e-mails often.
This project is meant to be a pleasurable way for everyone to apply their technical skills and learn something in the process.
The plan: to launch a meteorological balloon filled with Helium in the high atmosphere to gather data (temperature, pressure, altitude, photos)
The objective: to recover the balloon's payload at the end of the mission
The date: the tentative launch date is Saturday April 5th 2008
Side effects: Everyone involved will learn more about SPOTs and the other aspects related to the balloon launch. The progress blog will show our progress to the public. The code base and circuits will be available on Java.net. The video of our team doing this will be on YouTube. This is a great way to have a high-impact SPOT project in the limelight.
I would like to emphasize that recovery of the payload should be more important than breaking any psychological limit of "greatness". If the balloon has to abort at 15km altitude instead of 25km to be recoverable, then so be it :)
Up to now, I have planned the major logistical aspects, but from now on, It would be nice if you all participated with your insights and ideas. However, let's not get stuck with "Analysis Paralysis" in the process :)
On the Launch Date, we will be doing the following:
1- Go to a launch site (TBD)
2- Launch the balloon with its payload
3- Track the balloon visually using a telescope ("Base team")
4- Track the balloon using the internet ("Base team" and everyone) via APRS (APRS = GPS over radio modem, basically) packets transmitted on the 2m amateur band and received by stations around the region.
5- Track the balloon by car, using a radio and laptop listening to the Balloon's signal and the base team's visual tracking cues. This will be the "Chase team".
6- Recover the balloon.
After recovery, data from the payload will be analyzed and some more fun will ensue :)
The balloon will be a meteorological balloon filled with Helium to which a parachute and a payload will be attached. At a certain point during transit, the payload will separate from the balloon and fall back to earth while slowed-down by the parachute.
The payload will contain:
* Sun SPOT with eDEMO and eBALLOON boards
* Telit GM862 GPS/GSM module with antennas, even though cell phone coverage might be non-existent (http://www.sparkfun.com/commerce/product_info.php?products_id=7917)
* MicroTrak 8000FA Tracking radio and antenna (http://www.byonics.com/microtrak/mt8000fa.php)
* Olympus FE-115 Digital camera with Lithium AA batteries
* Temperature probe
* Absolute pressure sensor
* GPS/GSM Module and Cut-off system battery (Li Ion, 3.7V, 2000mAh) (http://www.sparkfun.com/commerce/product_info.php?products_id=8483)
* Radio battery (NiMH, 9.6V, 2000mAh)
* Radar reflector with at least 3m of Radar Cross Section in the S and X bands
* A buzzer to help in recovery
For the balloon cutoff, a heating element made with Nichrome wire will melt the balloon's retaining cord when a signal is provided.
The location of the launch, in my opinion, should be in a remote area very much to the WEST of the central valley, with a goal of forcing a balloon touchdown in the central valley, where the likelihood of recovery is much higher than in more mountainous regions.
The payload container itself should be made out of insulating material or filled with insulating foam to ensure a good resistance to the lower temperature of the higher atmosphere. The design has not been done yet and it is a big task that remains to be assigned.
The electronics are currently being designed. The eBALLOON board is designed and the routing is 40% completed after one evening of work. The GPS/GSM module carrier board is designed on paper and will be done rather quickly after the eBALLOON board. PCBs will be ordered in Bare Copper early next week. Together, these board will provide:
* A high-resolution ADC to acquire the absolute pressure sensor
* Open-drain outputs to drive the camera controls
* A high-current low-side switch for balloon cutoff
* The necessary circuits and connections to allow the GPS/GSM module to work
* A buzzer driver
* UART connections for the GPS/GSM module and the Tracker radio
* 1 Megabyte of Flash memory to record the experimental data
Items that go in the payload container have been weighed to help in designing the entire assembly. You can get the information at:
http://spreadsheets.google.com/ccc?key=pr4wZ62yujhaToDBAH2ZGVg&hl=en
The digital camera is already disassembled and on first analysis, it should be rather easy to hack to to serve our purposes.
For those of you wondering about the legality of such a balloon project, I would like to point you to two ressources:
* FAR-101: FAA Regulations regarding Kites, Moored Balloons, Unmanned Rockets and Unmanned Free Balloons (http://ecfr.gpoaccess.gov/cgi/t/text/text-idx?c=ecfr&rgn=div5&view=text&node=14:2.0.1.3.15&idno=14)
* Typical Balloon Mission FAQ, contains a lot of practical info about organising a launch (http://balloons.space.edu/habp/typical/)
There are also several projects that are similar in scope to this that are well documented:
* http://vpizza.org/~jmeehan/balloon/
* http://sunsite.utk.edu/~mcoffey/ux-1/
* http://www.natrium42.com/halo/flight2/
The rest of the info can be found at:
http://www.eoss.org/pubs.htm
This last link contains pretty much everything one would want to know about the topic.
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All in all, I feel like this is a project with reasonnable chances of success.
What is still unknown (please help !):
* Design of the payload bay and final weight of the assembly
* Final size of the balloon (dependant on previous point). I might purchase a larger balloon than the one I currently have, just to make sure.
* Parachute size, also dependant on payload size. Parachutes from Public Missiles Limited (https://blastzone.com/pml/components.asp?groupid=13), most likely 24" or 36".
* NAME for the mission.
* Exact Launch Site. Different scenarios can be tried with the following Online Balloon Path Calculator, which uses NOAA wind data and Google Maps (http://nearspaceventures.com/w3Baltrak/readyget.pl). Other software is at: http://www.eoss.org/balsoft.htm
* Duty cycle of sensor acquisition and radio downlink
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Software tasks that need to be done AND tested on the ground:
* GPS interface (Lachlan is working on it)
* Conversion of WGS84 (Latitude/Longitude from GPS) to a "flat" datum so that the software can easily figure "how far from the launch site we are" (polar coordinates). This will be used to force a cut-off of the balloon if it strays too far.
* GSM module interface to send SMS messages of GPS position.
* Code to serialize the data acquired to an AT26DB081 Flash chip (same chip as on the eDAQ board). REALLY IMPORTANT. This is similar to the SD card flash chips, but not quite the same commands and SPI-only.
* Camera interface module
* Data acquisition code
* System integration
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There are also some items that still need to be purchased or borrowed:
* Maybe a bigger balloon
* Parachute
* HELIUM :)
* PCBs and parts for PCBs
* Payload bay and misc hardware
* Nylon cord (at least 50lbs break strength, but not much more)
* TNC (packet modem) for chase team reception of APRS signal
* Mobile 2m radio (x2: base team and chase team)
* Automobiles
* Telescope (With azimuth and elevation readouts)
* AC Inverters to power a laptop in a car
* ???
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So that is all, friends :) Things will be moving pretty quick. Someone still needs to setup a blog and a Java.net project. I don't really have time for it, given that I'm working all I can on the electronics for the payload. I think it would be a good idea if several people participated to the software effort, and it would give us more time to test it on the ground some.
I hope most of your questions for what the project is about have been answered. I hope to hear back from each of you !
Best regards,
Tennessee Carmel-Veilleux
-- Main.arshan - 23 Mar 2008
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