GPS & Tracking

HAB Guide

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GPS & Tracking


Need to Know

There are many ways[1] to track your balloon as it ascends, or at least to find out where it landed when everything is all over. Your options and capabilities expand as you are willing to spend more time and money. At the very least you should use a GPS Messenger (SPOT or inReach) that will use a GPS signal and satellite communication to tell you where your HAB landed. With a bit more effort you can include APRS (Automatic Packet Reporting System) that will continually broadcast basic information about your craft, at least including GPS location. For the very motivated, there are various systems that you can put together with more sensors and/or radios that will deliver rich information throughout your flight from any of a variety of platforms. On top of this, there are many options for customization and built-from-scratch subsystems.


Using a phone to track the balloon is illegal.[2] Besides being illegal, it is also unreliable because it requires reception.


Using a Satellite GPS Messenger

You are going to need some kind of location-reporting device in your payload and a GPS messenger can be a great off-the-shelf option. These devices are going to be quite reliable at what they do because they are rigorously tested consumer- or even commercial-grade devices. They are also self-contained so “integration” with your payload can hardly be easier. There are web interfaces for you to monitor their travel across the surface of the Earth from basically any Internet-connected device and, since they use satellite communications, they will work as long as they have some view of the sky, anywhere in the world.


Some drawbacks are that there is no way to transmit any other kind of telemetry or other status data from your payload through these devices. You also pay a premium for the services they provide via the satellite communications service that they use. The systems’ modes of operation may also not be perfectly understood. For example, what happens if the device gets too cold, hits the ground very hard, or has some other operational issue? The tracking “rate” of these devices is somewhat limited and you cannot store their output to storage on your payload for a later, high-resolution look at the craft’s path.


Many HAB missions have used only one GPS messenger and have been successfully tracked and recovered. However, I personally know of a mission that used two tracking systems only to find that the GPS messenger was the one that failed for unknown reasons.


+--------+---------------------+-------------------+-------------------+
|        | SPOT Gen            | SPOT Trace        | DeLorme inReach   |
|        | 3[3],[4]            | [5],[6]           | SE[7]             |
+========+=====================+===================+===================+
| Ha     | \$150               | \$100             | \$260 (old        |
| rdware |                     |                   | version)          |
| Cost   |                     |                   |                   |
+--------+---------------------+-------------------+-------------------+
| Fe     | Moderate            | Minimum           | Most              |
| atures |                     |                   |                   |
+--------+---------------------+-------------------+-------------------+
| Just   | \$180/year (paid    | \$180/year (paid  | Approximately     |
| One    | monthly). One-year  | monthly).         | \$50. That is     |
| Month  | minimum term.       | One-year minimum  | \$25/yr to stay   |
| or     |                     | term.             | active and then   |
| M      |                     |                   | \$15/mo and the   |
| onthly |                     |                   | cost of           |
|        |                     |                   | individual        |
|        |                     |                   | messages.         |
+--------+---------------------+-------------------+-------------------+
| One    | \$150/yr            | \$150/yr          | \$20 one-time     |
| Year   |                     |                   | activation and    |
|        |                     |                   | then \$12/mo.     |
|        |                     |                   | That is, \$164    |
|        |                     |                   | the first year    |
|        |                     |                   | and \$144/yr      |
|        |                     |                   | after that.       |
+--------+---------------------+-------------------+-------------------+
| Bottom | \$300 is the        | \$250 is the      | Approximately     |
| Line   | minimum if paid at  | minimum if paid   | \$310 is the      |
|        | once and that will  | at once and that  | minimum cost to   |
|        | cover you for one   | will cover you    | use for a month,  |
|        | year. After that it | for one year.     | including         |
|        | is \$150/yr. I      | After that it is  | hardware cost.    |
|        | can't justify       | \$150/yr. Not     | Your initial      |
|        | buying this when    | good for          | purchase price is |
|        | the DeLorme offers  | wilderness        | higher with the   |
|        | much with little    | adventures in its | advantage that    |
|        | increased cost in   | second life but   | the device has    |
|        | most cases.         | this is the       | many other uses   |
|        |                     | cheapest option   | and then          |
|        |                     | but not by as     | subscription fees |
|        |                     | much as I'd hope  | are very          |
|        |                     | considering the   | competitive       |
|        |                     | lack of features. |                   |
+--------+---------------------+-------------------+-------------------+
| Ope    | -22 °F to +140 °F   | -22 °F to +140 °F | -4 °F to +140 °F  |
| rating |                     |                   |                   |
| Tempe  | (-30 °C to 60 °C)   | (-30 °C to 60 °C) | (-20 °C to +60    |
| rature |                     |                   | °C)               |
+--------+---------------------+-------------------+-------------------+
| Ope    | -328 ft to 21,320   | -328 ft to 21,320 | Not found         |
| rating | ft (-100 m to 6,500 | ft (-100 m to     |                   |
| Alt.   | m)                  | 6,500 m)          |                   |
+--------+---------------------+-------------------+-------------------+
| Usage  | "The transmitter    | "The transmitter  | Not found         |
| Notes  | (located underneath | (located          |                   |
|        | the SPOT logo)      | underneath the    |                   |
|        | needs to have an    | SPOT logo) needs  |                   |
|        | unobstructed view   | to be pointed     |                   |
|        | of the sky, either  | toward the sky,   |                   |
|        | outdoors or in a    | either outdoors   |                   |
|        | glass-enclosed area | or beneath        |                   |
|        | such as a vehicle   | fiberglass,       |                   |
|        | dashboard."         | fabric or glass"  |                   |
+--------+---------------------+-------------------+-------------------+
| User   | See footnote[8]     | See footnote[9]   | See footnote[10]  |
| Guide  |                     |                   |                   |
+--------+---------------------+-------------------+-------------------+
| Online | Yes                 | Yes               | Yes               |
| Tr     |                     |                   |                   |
| acking |                     |                   |                   |
+--------+---------------------+-------------------+-------------------+


Table 1 GPS Tracker Comparison


SPOT Gen3 and Trace

SPOT has some good options. The SPOT Trace is intended to help you keep track of things like boats. Basic tracking is every 5-60 minutes (you pick) while Extreme Tracking allows you to go down to every 2.5 minutes. The devices will transmit as long as there is motion, but the activation threshold for “motion” is unclear.[11] Based on others’ experience using the SPOT Gen3 for their HAB mission I accept that it is sufficient most of the time. I would be very concerned about “most” of the time versus “every” time but I do not have the data to take the analysis any further.


If cost or waste is a concern, and you don’t want to use it all the time, then finding someone that has one of these devices could lend it to you with your promise to replace it if lost or damaged.


Based on the company’s descriptions, it seems that the SPOT messengers require a clear sky view to the top of the device, so many high altitude balloon missions include gimbals that are custom-built[12] to keep the messenger pointing upward. I feel that if you are coming down under a parachute and transmitting every 5 minutes, then the device can only be so far from its last reported position, even if it happens to land sideways or upside-down so that it cannot establish contact with the satellites passing overhead.


DeLorme inReach SE

This is a strong GPS messenger while also being an amazingly capable device for wilderness adventures. The DeLorme (“du-LOR-um”) inReach SE is the lower level of the inReach family, with the other option being the inReach Explorer. Both have also had major redesigns around early 2017 so there is an opportunity to spend more for a very modern device or save on a slightly older device, your choice.


This device also has its unknowns, like operating at altitude and sky view requirements. I do know that if the device turns off for any reason (not that this should happen) then you must press the power button by hand to turn the device back on. One encouraging piece of technical information is that the device can run while plugged into external power. The device usually runs off of an internal LiPo (Lithium-Polymer) battery, and since keeping batteries warm is one of the biggest challenges of sending payloads to near space, it could be a very nice advantage to power the inReach from an external power source where you have more carefully managed the thermal operating environment. I suspect the device could run at even lower temperatures than it is rated if it is running on external power.


Footnotes

[1]: https://community.balloonchallenge.org/t/current-gps-tracker-products/668

[2]: http://www.highaltitudescience.com/pages/federal-communications-commission-22-925 points to the e-CFR that says this is illegal, which is 22.295 at http://www.ecfr.gov/cgi-bin/text-idx?SID=3a6f5c68673c71cf564f7db91144bafe&mc=true&node=pt47.2.22&rgn=div5#se47.2.22_1925

[3]: Product page at http://www.findmespot.com/en/index.php?cid=100

[4]: Rates at http://www.findmespot.com/en/index.php?cid=103

[5]: Product page at http://www.findmespot.com/en/index.php?cid=128

[6]: Rates at http://www.findmespot.com/en/index.php?cid=129

[7]: http://info.delorme.com/

[8]: http://www.findmespot.com/downloads/SPOT3_User_Guide.pdf

[9]: http://www.findmespot.com/downloads/SPOT_TRACE_User_Guide.pdf

[10]: http://www.inreachdelorme.com/assets/pdf/DeLorme_inReach_Brochure.pdf

[11]: http://www.findmespot.com/en/index.php?cid=111

[12]: https://sites.google.com/site/ucsdnearspaceballoon/previous-launches/january-15-2011-zp and https://sites.google.com/site/ucsdnearspaceballoon/documentation/spot-ball-construction-tips


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