Picture of Low-cost Near Space Without HAM Radios or Cellphones
After researching near space balloon projects and launching two of my own I've found that the major hurdle is in communication with the balloon payload. Many near space ballooners are using HAM radio equipment to track their balloons through triangulation or APRS data transmissions. That's all well and good if you have a HAM license and the experience to know what equipment and frequencies to use. The non-HAM ballooners are using cellphones or cellular modules to send SMS messages for tracking the flight. Cellular modules work pretty well up to 40k feet altitudes with good external antennas, but above that altitude there will be no communication from the payload. It's a bit nerve racking not knowing what's going on with the payload for more than half of the flight. Cellular coverage isn't always available in the best launch locations in the U.S.

I discovered that the communications challenge is very simple with the right hardware. The XTend900 radio from Digi (http://www.sparkfun.com/products/9411 ) and a high gain patch antenna (http://www.l-com.com/item.aspx?id=20447 ) can keep you in communication with the payload for the entire flight and can even provide enough bandwidth to transmit small pictures. This instructable will focus on the minimum set of hardware to get you into near space, capture those spectacular photos, and track your payload to recovery.

For information on my last near space flight, Night Sky, visit www.wildfirerobotics.com/nightsky
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JoshuaM110 months ago

So the GS407 is now discontinued. Any alternate advice you might recommend? I assume hookup will be different as well... Great work by the way!!!

NearSpaceLuke (author)  JoshuaM110 months ago
You'll have to do your homework on this one. The U-blox chipset allows you to get position above 60k feet. That's really the only thing you need to find in the new GPS receiver. Good Luck!
007dna11 months ago

Hi, great ible. Quick question: I am wanting to have a photo stream transmit to me from the balloon during flight. I am very new to this area, what do I need for that? I assume I can't just hook up a camera to the breakout, I need to connect it to a Pi or Arduino. Also, what is the point in having the radio module on the ground? You are not transmitting TO the balloon, so all you should need is just a receiving antennae....

Help is greatly appreciated, thank you.

NearSpaceLuke (author)  007dna11 months ago
I give the same advice to everyone doing this for the first time. Keep it simple, or you'll lose a lot of expensive equipment. Balloons seem very simple, but you'll be panicking on launch day. Launch your first balloon with just the tracking information coming at you. Once you can track and find your balloon on the ground, then move on to multiple data streams.

When you get to trying to transmit the picture, you'll find you need to convert the picture to a serial data stream. That is going to be a lot of data, and the data rate you get over a 40+ mile radio link is very slow. You're not going to be getting real time video or more than a picture a minute with inexpensive radios. Do your research on picture formats and baud rates. A little math will tell you just how long it takes to transmit a picture.

As for having a transciever on the ground, it was easy to write the firmware once and use the same module on the balloon and on the ground. Keep it simple, reuse known equipment and code, things will fail on launch day, and with some luck you'll find your first balloon.
afry21 year ago

I am running through these links and I have come across a bad one. Is there a website that I can be directed to instead of


NearSpaceLuke (author)  afry21 year ago


cvsa1 year ago

That tracking software you use it is accurate? I am North West of you in Southern BC. I have played around with this other website but it gave me a completely different flight path from the one that you use. I figure if it is accurate for you it should work for me here too.


Great instructable!

NearSpaceLuke (author)  cvsa1 year ago
I found their prediction to be right on the money. What wasn't on the money was my ascent and descent calculations... The balloon ended up traveling twice the distance over ground because the ascent rate was half what I planned for.

Wind patterns at different elevations and different locations are extremely variable. You should run predictions right up to your launch date just to see what might happen if something changes.

Good to know. Any suggestions on adjusting for the ascent rate? Don't want to get caught in the mountains before I clear the valley bottom.

NearSpaceLuke (author)  cvsa1 year ago

My ascent rate was 16.5 ft/s, which seemed to be half of what the prediction expected. If you can't get your balloon to the 33 ft/s that the model expects, then you should find a different predictor that you can adjust the ascent and descent rates. It's always good to get a second opinion, so using two models from different sources is a good idea anyway.

Thanks again.

aallar1 year ago
Also would the RFD 900 Radio Modem work instead of the xtend 900?
NearSpaceLuke (author)  aallar1 year ago
Looks like a good radio. I haven't used the RFD900, though. It has enough output power and TTL serial interface, which are the most important things for this application.
aallar1 year ago
I have this for my gps would this work work instead of the GS407? 
NearSpaceLuke (author)  aallar1 year ago
The description says it has been tested up to 88k feet altitude. I can't say for sure that it will work, but it seems like that should do for you.
rdx2272 years ago
Hello, I'm slightly confused as to which parts go onto the payload and which stay on the ground. From your descriptions I got:
- 1 GS407
- 1 breakout board w/ resistor
- 1 battery
- 1 antenna
- 1 XTend 900 radio module
- 1 uUSB-MB5
- 1 breakout board w/ resistor
However, the numbers don't match up and I can't seem to find where/how the second XTend 900 radio module connects. Any mention of the XTend 900 radio module only refer to it being connected to the PC. Could you please clarify?
If I follow the numbers you give in step 9, would that would suggest that the second antenna is on the ground connected to the XTend 900 radio and the second XTend 900 radio is in the payload, connected to the antenna (by the way, does that connection need an adapter?) and the breakout board. Since the GS407 also needs to be connected to a breakout board, do they share one?
Thank you
NearSpaceLuke (author)  rdx2272 years ago
Step 2 says that you need to solder the wires from the GS407 to the XTend breakout board. I assumed you'd know to plug in your second XTend radio to that breakout board. You'll have this set of connections when you're done:
Balloon payload:
-GS407->XTend breakout->XTend radio->antenna

Ground Station:
-Antenna->XTend radio->XTend breakout->uUSB-MB5->Computer
omass2 years ago
Hey! Great tutorial but I was wondering- how could get immidiate data transactions?
If you live on a small island, it tends to fly into the sea :P Any suggestions will be appreciated!
NearSpaceLuke (author)  omass2 years ago
There won't be a way to stop it from flying into the water, unless you plan on a payload that can fly itself back to you (this is illegal in the U.S. without impossible to get waivers from the FAA).

You can increase the rate of NMEA messages from the GPS reciever to 5 per second on the GS407. Your best bet, if you must launch from an island, is to make your payload waterproof and buoyant. Do very careful flight plan predictions, fill your balloon precisely to get the rate of ascent right, pick your parachute for proper rate of descent, and get a fast boat so you can be at the landing zone before the payload lands. If you make the payload so it floats with the antenna facing up, you should be able to receive the signal well over a mile away from the payload. If the antenna is under water...you'll never hear from it again.

Might be cool to make the payload an autonomous boat that drives itself back to the closest shoreline.
jkarimi2 years ago
what was the peak altitude that your gps module was able to function at? Many of the devices I see on spark fun show that they have an upper limit of 18,000 ft due to COCOM regulations. Also the module you used is retired however there is a new model GS407, will the Airborne adjustment work on this new model?
NearSpaceLuke (author)  jkarimi2 years ago
The altitude measurements aren't actually limited by regulations and neither are the speed of movement...unless you plan on exporting your device outside the country (this statement is sure to get a bunch of comments from armchair experts). Using the dynamic platform setting of <2G airborne for the GS407 I had, you can get altitude readings from ground to the maximum theoretical GPS altitude.

With the new GS407, the setting is the same <2G airborne, but it is no longer under the NAV section. It's now in the NAV2 or NAV5 depending on the firmware version you have. You'll still see the NAV, NAV2, and NAV5 sections with any firmware version, so the easiest thing to do is set it in all three. Then it's done and you didn't have to worry about reading out the firmware version.
buckeyeguy2 years ago
How about an update on connecting the GPS with the new model GS407. It doesn't look like the same connectors are available to solder to? I'm pretty much electronically challenged, so figuring it out is way beyond me.
NearSpaceLuke (author)  buckeyeguy2 years ago
Ok, so it's a bit easier now actually. The GS407 uses a better connector and Sparkfun is offering cables with the connector attached. Get yourself one of the cables. Then clip off the connector that you don't need, strip the wires for TX, RX, VBAT, and GND. Then follow the rest of the instructions in this instructable using those wires. You can see the pinout of the connector in the GS407 datasheet on page 4. Pin 3 -> RX, Pin 4 ->TX, Pin 6 -> VBAT, Pin 1 -> GND.
Dear NearSpaceLuke,
I am an AP Physics teacher. I want my students to do this as a class project. I will get all the materials then they will follow your instructions. Do you think 17-18 year old students would be able to complete this project?
Thanks in advance for your advice.
NearSpaceLuke (author)  CaPhysicsTeacher2 years ago
This is a good project for 17-18 year olds until the balloon gets in the air. Small balloons take about 4 hours to launch, track, and recover. The kids will probably get tired of waiting for it to land. If you aren't paying attention to the balloon and following it closely you may not be able to recover it.
ninfan12 years ago
Hello everyone. I've been researching and preparing for my first launch for weeks and recently have been scouting launch and landing sites. I'm working with the CUSF Landing Projector program now and have a minor question. When inputting my launch date, it already shows the date one day ahead of where I'm located now (I live in Florida ). I'm having a few issues converting EST to UTC time when it crosses over to the next day. For instance, if it's 9 pm here in Florida right now and I'm planning on a 10 am launch, what would I need to do. How far ahead will the program let me predict? Thank for any insight.

** I'm just running simulations to get used to the program for now as I research and build my payload etc. I do seem to be able to run current simulations if I leave the date as it is and launch tiem by default.
ninfan1 ninfan12 years ago
In regards to the CUSF Landing Predictor, I'm following the step by step instructions I saw on this page and inputting my payload weight info etc correctly I believe. The projector y path and landing site look correct, but when compared to the wind directions I see on local Dopler it seems to be going to wrong direction. Is this normal, or am I doing something wrong. Local wind directions are out of the NE which I would think would make my payload travel SW. Thank you for any insight.

ninfan1 ninfan12 years ago
Ok, so I apparnetly was not looking at the jetstream wind direction! Looking closer at my projected path, I now can see the lower level winds effecting the path correctly and then the upper level winds taking over. Learning more each day:

robotkid2493 years ago
If you're interested my new instructable on near space balloons is published!

Dg6133 years ago
Hi nearspaceluke

It would be great if you help me build the tracker. I am based in Australia and would love your input.

Up to it?
tstowe3 years ago
Here is a better site: http://nearspaceventures.com/w3Baltrak/readyget.pl
NearSpaceLuke (author)  tstowe3 years ago
I actually don't like that site at all. The predictions come out just fine, but the user interface is garbage. The plot track to Google Maps never works, either.
That's the only one I use. It's usually VERY accurate. I've had it the prediction be off by less than a mile. I also like that you can look at the raw data and see lat., long. and alt. throughout the prediction (so I can compare it to the actual numbers during the flight).

I also don't think I've ever had a problem looking at the prediction in Google Map.
Is there a reason why you are using helium, rather than hydrogen, as the lifting gas? I kinda thought that H2 would be cheaper, and provide more lift for the same volume balloon, but maybe there's some other reason, like maybe your local welding store won't sell you hydrogen.  Just curious about that part, I mean your choice for lifting gas.
NearSpaceLuke (author)  Jack A Lopez4 years ago
Hydrogen is probably cheaper, and it is a marginally better lifting gas. It's also exponentially more dangerous than helium. Sellers in my area don't like to sell in large quantities to amateurs and the tiny bit of extra lift isn't really worth the added dangers in my mind.

However, I'm thinking about making a rockoon in the near future. The balloon would lift a rocket to altitude and then the rocket would shoot right through the balloon. It would be crazy awesome to see a giant hydrogen explosion as the rocket goes through the balloon!
Actually, the probability of it actually exploding is very high because Hydrogen is one of the alkali metals (not exactly.)
I wouldn't say the probability is high. It will burn. If mixed with oxygen it will explode. But for either of these to happen there has to be an open flame or a spark. Don't smoke and ground everything.
Remember what happened to the Hindenburg???
Yes, and remember what has happened to the dozens of other groups who do high altitude balloon flights and use hydrogen all over the country....nothing. A pencil is dangerous if you don't use it correctly.

I've done five high altitude balloon launches (www.thetalon.smugmug.com/misc/space). If you use it safely, there's nothing wrong with using hydrogen. It's cheaper (a cylinder rents for $60. The same size helium is over $100) and it has more lift by volume. We are looking at doing a flight to break the altitude record in June. If we try it, we will be using hydrogen.
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