What is a high-altitude balloon?

A high-altitude balloon is a large balloon filled with a light gas such as helium that carries a package of weather sensors (called the payload) up through the atmosphere. These sensors measure things like temperature, humidity, air pressure, and wind speed at different heights above the ground. The data that is collected can be analyzed to help us better understand what is happening in the atmosphere.

What is the difference between a high-altitude balloon and a weather balloon?

There really isn’t any difference. A weather balloon is a type of high-altitude balloon that simply carries meteorological sensors high into the atmosphere. You can send up a high-altitude balloon without meteorological sensors, of course. In that case, you would just call it a high-altitude balloon and not a weather balloon.

What is the balloon made of?

The balloons that we use are made out of a stretchy material called latex.

How big is the balloon?

When we launch, the balloon is usually about 8 feet wide. However, as it rises high into the atmosphere it expands to about 25-30 feet wide (larger than a small school bus!) before it finally pops.

How much does the balloon cost?

Most of our balloons cost anywhere from $75 to $150 each, depending on size.

How high can the balloon ascend?

The weather balloons we use can reach heights of over 100,000 feet (19 miles!) above sea level, where the air pressure is about 100 times lower than it is at sea level. This is well into the stratosphere, the next layer of the atmosphere above us. Currently, the highest balloon we have launched in Wyoming went up to over 110,000 feet. However, this is well below the world record of 173,000 feet set in 2002 in Japan.

How far can the balloon travel?

This depends mostly on how strong the winds are high in the atmosphere in a region we call the jet stream. During the summer, the winds in the jet stream are usually pretty weak, so a weather balloon might land only 20-30 miles away, perhaps even closer. In winter, the jet stream can sometimes be very strong and carry balloons as far as 100 miles away or more!

How long does a high-altitude balloon flight last?

From launch to land, our balloon flights usually last for 2-3 hours. It typically takes anywhere from 90 minutes to about 2 hours for the balloon to reach its maximum altitude and burst. After that, it takes another 30-45 minutes for the payload to fall back to earth.

Why does the balloon pop?

Before we can answer this, we must think about air pressure. The air pressure at any location is basically the weight of all the air that is pushing down from above that spot. At the ground, the entire atmosphere is pushing down from above so the air pressure is highest. Up in the atmosphere closer to space, there is less atmosphere above, so the total weight of the air above is less and air pressure is lower.

When the balloon is at the ground, the pressure from the helium on the inside of the balloon is balanced with the air pressure pushing back on the outside. This is what gives the balloon its size right before we launch it. As the balloon goes up through the atmosphere, the amount of helium inside stays the same (unless there is a leak) but the pressure from the air on the outside is slowly getting weaker. In other words, the outside air is pushing back less and less against the helium, so the balloon is able to expand to reach a balance.

Eventually, the balloon reaches the limit to how much it can expand and it pops (or bursts, as we like to say). Once this happens, the payload no longer has anything to carry it upward and therefore begins to fall back to earth.

Can we see the balloon pop high in the atmosphere?

If there are no clouds overhead and the sky is nice and blue (i.e., not hazy or smoky), it is possible to see the balloon with the naked eye when it is at 100,000 feet. This happens for maybe 10-20% of our launches. It looks like a tiny white speck that is impossible to see unless you are actually looking for it. The best chances of seeing the balloon at these altitudes is when the balloon is away from the sun. If you can keep your eyes locked on the balloon, it will suddenly disappear when it pops. We have only witnessed it popping a couple times, but it was quite incredible!

Why can't we touch the balloon with our bare hands?

All of us have oils in our skin that help keep our skin moist. Our hands are especially oily. If someone were to touch the balloon’s thin, stretchy latex with their bare hands, they would get a little bit of that oil on the balloon. This is no big deal at first, but as the balloon rises through a part of the atmosphere with temperatures below freezing, the oil they left on the balloon will freeze and prevent that part of the balloon from expanding any further. The rest of the balloon, however, will continue to expand, causing the balloon to eventually take on an irregular shape. This could cause the balloon to burst earlier, and at a lower altitude, than it is supposed to. To prevent this, we try to always wear gloves on our hands whenever we have to touch the balloon.


What payloads do we send up with the balloon?

The standard items that we typically send up with a balloon are: (1) a parachute, (2) a GPS tracking unit called the SatCom that is equipped with meteorological sensors to measure temperature, air pressure, and relative humidity, (3) several HD video cameras, and (4) two backup GPS units. We also give students and teachers the opportunity to send their own items and experiments up with the balloon as well. These items are carried in Styrofoam payload boxes. All of these items together are considered the balloon payload. The payload items are connected to each other and to the balloon through a system of harnesses and high-strength cords.

Can you tell me more about the SatCom?

The SatCom, or Satellite Communication device, is a GPS tracking unit that is also equipped with meteorological sensors and a number of other bells and whistles. It can also calculate the wind speed and direction based on changes in its GPS position over time, assuming of course that the entire payload is moving with the wind. The SatCom is designed and maintained by Stratostar, an education company also focused on high-altitude ballooning and K-12 science outreach.

During flight, the data from the GPS and meteorological sensors are transmitted to the satellite network once per minute and immediately send to the internet. This allows us to track the balloon’s location and monitor the onboard data in real time as the payload ascends and descends through the atmosphere! You can check out the data feed from a launch this past summer in Douglas, WY by clicking here.

Can you tell me more about the meteorological sensors on the SatCom?

At this time we do not have specific details on the sensors or how they function. It has been our experience that the air pressure sensor provides the most accurate and consistent measurements. The temperature sensor measurements are often 20-25°F too warm, especially higher in the atmosphere where actual temperatures are -60°F or lower. However, they are often more accurate near the ground and when not in direct sunlight. It seems that the humidity sensor measurements also tend to be a bit lower than they should be, although accurate humidity measurements are notoriously difficult to obtain.

Overall, our suite of sensors still does a fine job of showing how these meteorological variables change throughout the atmosphere. We often use these data to teach students about different layers of the atmosphere, the jet stream, clouds, etc.

Can you tell me more about the video cameras?

Prior to 2019, we used a set of Contour Roam HD cameras that provided us with decent HD video quality up to 1080p resolution and 30 frames-per-second (FPS). However, in 2019 we upgraded to some brand new GoPro HERO5 Session cameras. Although we still typically record at 1080p resolution, we are now able to do so at a smoother 60 FPS and with much improved image and sound quality. We find that these settings tend to give us fantastic video quality while still preserving both battery life and memory card space.

By themselves the battery life on these GoPros is rather poor, so we connect each to an extended battery pack that usually allows for up to 3 hours of recording time. This means we can usually get everything from launch to landing on video! Even with the battery pack, each camera is super lightweight (about 5 oz), making them perfect for our launches. For a typical launch, we’ll send up three cameras: one pointing up at the balloon, one pointing sideways at the horizon, and one pointing down at the ground.

What do you do with the video footage?

Following each launch, the footage obtained by the three cameras onboard the balloon payload is downloaded and backed up to our computers. For our new GoPro cameras, the total size of this footage (6+ hrs @ 1080p resolution and 60 FPS) can be in excess of 100 GB!  If participants would like copies of these raw unedited video files, we are happy to provide them. However, for most launch events – especially those involving K-12 students – we typically create a short (~5 minute) highlight video and upload it to our YouTube channel.

Can you tell me more about the backup GPS devices?

For each launch, we send up two SPOT GPS Messenger devices as a backup in case our primary tracking device, the SatCom, fails during flight. Our SPOT devices send the location of the payload to the internet (via satellite) once every 10 minutes. On a full battery, they can continuously track and transmit their locations for several days. Thus, if we can’t recover the payload right away and have to come back at a later time, or if the SatCom fails, we will still be able to get location updates for quite some time after the payload has landed.

Our SPOTs work best when they are facing the sky. Otherwise, they will have difficulty communicating with the satellites or lose connectivity altogether. To ensure consistent satellite communication, we place the two SPOTs back-to-back into a small yellow box that is suspended from the bottom of our payload. This way, whenever the payload lands, at least one of the SPOTS will have a view of the sky.

What happens if we lose signal from all the GPS devices on the payload?

This would be a very unfortunate situation, since we probably would never be able to recover the payload. We have lost signal from either the primary or backup GPS devices in the midst of a balloon flight, but never from both during the same flight. If that were to happen, we would just have to hope that someone eventually find it and returns it to us.

Can I get the data that was collected by the meteorological sensors?

Certainly. We do not typically use this data ourselves, so we are more than happy to send you the data if you would like to use it.

Is there anything we are NOT allowed to send up with the balloon?

Yes! Although the FAA does regulate high-altitude balloon flights, their regulations are almost 60 years old and do not really specify what you can and cannot send up with a balloon. We have therefore made our own rules about this based on what we deem to be safe and reasonable. At this time, we do not allow our payloads to include live animals, highly flammable liquids, explosives, or any other items that are illegal to possess. In addition, the maximum weight of each individual payload item cannot exceed 6 pounds (per FAA regulations), meaning that you are not allowed to send up something heavy like a bowling ball.

Are there limits to how much the payloads can weigh?

Yes. Sort of. The entire payload (i.e., everything below the balloon) cannot weigh more than 12 pounds (5.4 kg), and no single payload item can weigh more than 6 pounds (2.7 kg). If you entire payload weighs more than 12 pounds, or a single payload item more than 6 pounds, then getting clearance from the FAA to launch your balloon becomes a little bit more complicated (see next question).

What are the FAA regulations regarding high-altitude ballooning?

You can read all about the FAA high-altitude balloon regulations here (see both Subpart A – General and Subpart D – Unmanned Free Balloons). Below is a basic summary.


  • A single payload package weighs more than 6 pounds
  • The entire payload (two or more packages) weighs more than 12 pounds
  • A single payload package weighs more than 4 pounds AND has a weight/size ratio of more than 3 ounces per square inch on any surface
  • The payload uses a rope or suspension device requiring an impact force of more than 50 pounds to separate the payload from the balloon
  • Flying your balloon creates a direct hazard to other persons or their property (includes intentionally dropping objects from the payload)


  • You cannot fly your balloon within certain restricted airspaces
  • You cannot fly your balloon if clouds are obscuring more than half of the sky
  • You cannot fly your balloon if the horizontal visibility is less than 5 miles
  • You cannot fly your balloon if it will pass over a highly-populated area during its first 1,000 feet of ascent
  • You cannot fly your balloon if its projected landing spot creates direct hazard to other persons or their property
  • You cannot fly your balloon at night unless both your balloon and payload are equipped with flashing lights visible for at least 5 miles
  • Your payload must be equipped with at least two independent cut-down systems or devices
  • Your payload must be equipped with an appropriate radar reflective device
  • You must provide appropriate advance notice of the launch to the nearest FAA air traffic control facility
  • You must provide any balloon position reports and other flight-related information that are requested by the FAA

For our launches, we do our best to comply with all the payload regulations, allowing us to be exempt from all high-altitude balloon restrictions.


How often do you do balloon launches?

We typically do about one balloon launch per month during the school year (January to May and September to December). We sometimes do a few launches over the summer as well. Click here to see a complete list of all the launches we have done since 2014.

Why do people launch high-altitude balloons?

We launch weather balloons as a way to bring real-world scientific activities to K-12 classrooms throughout Wyoming. However, the data collected by sensors on a weather balloon payload are extremely important to meteorologists, researchers, and weather forecasters. That is why weather balloons are launched every day by the National Weather Service at many locations across the United States. These data help meteorologists understand what is going on high in the atmosphere far away from all of our sensors on the ground. Data from these balloons are also used by computer forecasting models to simulate what might happen in the future.

Who else launches high-altitude balloons?

Lots of people! In fact, weather balloons are launched two times every day from more than 900 locations across the world. Almost all of these are launched at the same exact time: 00:00 and 12:00 Coordinated Universal Time (UTC). In Wyoming, that’s 6am and 6pm during daylight savings time (i.e., March to November), and 5am and 5pm during mountain standard time (November to March). In the United States, this is done by the National Weather Service at 92 of their offices. The only Weather Service Office in Wyoming that launches balloons is located in Riverton.

Scientists and other researchers sometimes launch weather balloons for their own research projects. Instead of using the data from these balloons to make forecasts, they use data to try and better understand how the atmosphere works. Ordinary citizens can launch weather balloons as well, if they can afford it. This seems to be happening more and more throughout the U.S. in recent years. You can see plenty of videos of ordinary citizens launching weather balloons on YouTube. Finally, there are other groups like us that launch weather balloons with college and K-12 students as part of their science outreach programs.

Can I launch my own high-altitude balloon?

Sure, there are lots of regular folks across the country that have become involved with high-altitude ballooning. There is obviously a cost involved, mainly for the balloon (~$100) and helium ($150-500, depending on how many cylinders you get and where you get them from). You will probably also want some sort of GPS tracking device (it cannot be your cell phone). The SPOT GPS units that we use as backups could potentially be used as your primary tracker. The newer version of these costs ~$150 and requires a monthly subscription for satellite access (~$20/mo). Folks that are more technologically savvy could build their own tracking device if they are so inclined. A decent resource for anyone interested in getting into high-altitude ballooning can be found here.

Is Wyoming a good place to launch balloons?

We think so! There are not many people that live here and a lot of the land is public so the chances of the payload landing on someone’s property or in a busy city are very low. Additionally, while we do have a lot of mountains here, we also have a lot of open areas and rolling plains, especially in the central and eastern half of the state. These areas are easier to hike into if that’s where the payload lands. Finally, since Wyoming is near the middle of the country we don’t have to worry about the payload landing in the ocean.

Will you launch anywhere in Wyoming?

No, there actually are a few locations in Wyoming where we won’t do a balloon launch. For example, we will probably never launch from the northwest part of the state (i.e., Jackson, Tetons, Yellowstone, etc.). The primary reason is because those areas are surrounding by mountains, and any payload we send up will most likely land in the mountains very far from roads. It would take a long time for us to be able to retrieve it, in grizzly bear country no less! To be able to have a successful launch and recovery from one of those locations, we would need to have absolutely perfect wind conditions high in the atmosphere, something that doesn’t happen all that often.

Do you launch balloons from outside of Wyoming?

No, at this time we only launch balloons at locations within Wyoming.

Do we have to let the FAA or airports know about our balloon launches?

If the payload complies with FAA regulations, then the quick answer is no. However, as a courtesy we have started informing the FAA any time we plan to launch relatively close to an airport (within ~5 miles or so). This is done by submitting a Notice to Airmen (NOTAM) ahead of time, which basically lets any pilots flying into or out of that airport know that you will be launching a balloon close by at a certain time. Again, it’s not required, but it’s a good idea when launching near an airport!

Can bad weather affect a balloon launch?

Absolutely! The most common weather-related reasons for postponing or canceling a launch are high winds and heavy precipitation (usually snow). In Wyoming, wind is most often the culprit. Winds over 15 mph can make filling a balloon very challenging, and winds over 25 mph can make launching the balloon nearly impossible (and potentially dangerous). We make postponement decisions on a case-by-case basis, but a forecast calling for high winds at the launch site or a significant amount of precipitation in the area will usually do the trick. Other non-weather-related factors can also have an impact on balloon launch postponements (see next question).

What other factors can affect a balloon launch?

Many things can go wrong before a launch that could force a postponement (e.g., problems with the GPS devices, a faulty balloon that bursts prior to launch, trouble getting helium, etc.). However, the most common non-weather-related factor that can impact a balloon launch is the projected landing location.

Landing locations that are deep in the mountains (especially during winter when the snowpack is deep), near large bodies of water, or far away from easily accessible roads can make it very difficult to retrieve the payload in a timely manner. Meanwhile, landing spots near large population centers can be problematic since we don’t want our falling payload to cause any hazards to people or property. Prior to launching, we always have a pretty good idea for where the payload will land, and if it looks problematic we will consider postponing the launch.

Can we launch a balloon near a thunderstorm? At Night? At sunrise/sunset?

Technically, the answer to all three of these questions is yes. However, we don’t launch near thunderstorms primarily because of the lightning hazard (both to the payload as well as to ourselves). We have not yet launched at night, although we have done one launch shortly before sunset. We have also done one launch shortly before sunrise. None of these are prohibited as long as your payload is exempt.

What is a tethered launch?

A tethered launch is basically a mock launch that we occasionally do when we don’t have the time or resources to do a full launch. Instead of sending a balloon and payload up to ~100,000 feet, we keep them tied to the ground with a 150-foot tether line. This allows participants to get an idea for how our launches work without us having to worry about recovering the payload. These types of launches work well for things like teacher workshop sessions and balloon launch trainings. They can also be a decent backup option for a full launch if we end up having to cancel the full launch at the last minute due to a poor predicted landing location or unfavorable weather.


What happens if the payload lands on private property?

This actually happens quite often, especially when we launch in the eastern half of the state. If a payload lands on private property, we will try as hard as we can to get in touch with the land owner. Sometimes this is quick and easy while other times it takes a lot longer (sometimes days or weeks). The vast majority of the time, we do eventually find the land owner and one of the following happens: (1) the owner grants us permission to drive or walk onto their land to retrieve the payload, or (2) the owner retrieves the payload and brings it to us. In rare cases, it isn’t clear who owns the land (if anyone does at all) or how we would go about contacting them. Those “gray area” situations require a lot more thought and consideration about what our options are, and we approach these on a case-by-case basis.

What happens if the payload lands in the mountains or in a lake/river?

We have had the payload land in the mountains before, requiring us to hike about 5 or 6 miles one-way to get it. As long as we know exactly where it lands, even if it’s many miles from a road, we will likely be able to go and retrieve it eventually. It might take a few weeks or months, especially if we have to wait for snow to melt, but we’ll be able to get it back.

We have not had a payload land in water, although we had one close call near Flaming Gorge Reservoir. If it were to land in water, most of our equipment is waterproof and would therefore survive. Most of it would probably float as well, so we suspect that we’d find it rather quickly and eventually figure out a way to get it out of the water.

What happens if you launch in Wyoming but the payload lands in another state?

This is not a big deal. We have had payloads land in Montana, South Dakota, Nebraska, and Colorado. Recovering the payload works the same way as if it had landed in Wyoming.

What is the longest/shortest distance you've had to walk to retrieve a payload?

The longest we’ve ever had to walk during a payload recovery back in 2016. That payload landed on public land in the Laramie Range southeast of Casper. To get to it, we had to park our vehicle to the north at a private ranch (with permission) and hike in about 5-6 miles on some old dirt roads. While it was quite memorable and scenic, we prefer much shorter hikes!

Speaking of shorter hikes, we have had payloads land on dirt roads, allowing us to drive right up to them. We’ve had payloads land a few dozen feet of off paved highways as well. While these types of recoveries are “textbook”, they are pretty rare. Most of the time, we have to get out of the vehicle and hike some distance (usually more than 1/2 mile) to find the payload.

Do you know where the payload is going to land before you launch?

We don’t know exactly where it will land, but we always have a really good idea of where it will go. Before the launch, we use the Balloon Landing Predictor from Cambridge University (yes, the one in England) to get an idea for what the flight trajectory of the balloon will be.  There are other balloon flight prediction websites out there too, but this is the one we utilize most often.

Basically, these websites use global weather forecasting models to get a forecast of the wind speeds and wind directions at various levels of the atmosphere for the time and location of your launch. Using some math, they predict the 3D trajectory of the payload as it ascends and then falls back to earth. On average, we have found that the predicted landing locations from the Cambridge University website (obtained right before the launch) are accurate to within about 5 miles. At best, it has been 1 mile off of the actual landing location. At worst, it has been 19 miles off. Overall, it gives us a good estimate for where the payload will land and helps us decide if it’s worthwhile to launch on that particular day.


Is helium safe to use?

Yes, helium is a non-toxic inert gas which means that it will not explode or catch fire. The only real danger of using helium for high-altitude ballooning lies in the fact that it is stored under high pressure (~2500 PSI) in metal gas cylinders. If its cylinder were to somehow rupture, the high pressure of helium inside could cause the cylinder to become a flying 120-pound projectile. Fortunately, such accidents are extremely rare. We always make sure to be very cautious when handling helium cylinders.

Can you use hydrogen instead of helium?

Yes we certainly could, but we probably never will. It is true that hydrogen gas has some advantages over helium for high-altitude ballooning. It is a lot cheaper, its supply is pretty much unlimited on earth, and it is lighter which means it provides more lift per volume. However, hydrogen is also extremely combustible and therefore quite dangerous to handle. For obvious safety reasons, we prefer to stick with helium.

Where do you get your helium?

Most of the time, we get helium through our chemistry supply room at the University of Wyoming. They obtain this helium from compressed gas suppliers like Airgas or Rocky Mountain Air Solutions. Occasionally, we may choose to order helium directly from local suppliers and have the cylinders delivered directly to the launch location. Otherwise, we have to transport the helium ourselves.

Aren't we running out of helium?

Not really. Helium is one of the most abundant elements in the universe, although it is somewhat rare on earth. However, our understanding is that there is still plenty of helium underground to last humanity for quite some time. Helium prices have indeed skyrocketed in recent years primarily due to the lack of helium availability. In other words, there is plenty of helium waiting to be retrieved, but we humans can’t retrieve it fast enough for the rising demand. If you’re interested in this topic, we suggest you read this article which explains the whole helium situation in a lot more detail.


When did the Wyoming Space Grant balloon program begin?

We started our balloon program in 2011. However, the program really didn’t get up and running until Fall 2014 when we did our first K-12 launch with one of the elementary schools in Laramie. Since then, we have been launching balloons with K-12 schools across the state about once per month.

How can I request a balloon launch at my school?

If you are a teacher or educator in Wyoming and would like to have us come do a balloon launch with your school or organization, you can fill out a balloon launch request form here. We cannot guarantee that we’ll be able to accommodate your request, but we will certainly respond and try our best to work you into our schedule.

What is a radiosonde? What is a sounding?

A radiosonde is a small instrument package sent up with a weather balloon that collects temperature, air pressure, and humidity data and transmits them by radio back to a ground receiver. However, our SatCom GPS device would technically be considered a rawinsonde, since it also provides wind measurements in addition to the other sensor data (rawinsonde = radio-wind-sonde).

In meteorology, a sounding is a set of weather measurements collected vertically throughout the atmosphere. Thus, the data we collect with our sensors as the balloon goes up constitute a sounding. These data can be plotted on diagrams that help us visualize how the atmospheric conditions change with height.

How cold does the air get during a balloon flight?

Very cold. It’s normal for temperatures higher in the atmosphere to be colder than -60°F and we have seen temperatures below -90°F.

What happens if the balloon or payload hits a plane?

This would be quite rare, but we do get asked this question a lot. We are not currently aware of any cases where this has occurred. In most cases, especially with larger airliners, the aerodynamics near the plane may help to push the balloon or payload around the plane and out of harm’s way. Smaller planes would probably be able to more quickly avoid a weather balloon if they saw it. If interested, you can read more about this topic here.

What if I have a question that isn't on this list?

If you have a question that wasn’t answered here, or would like additional information about our balloon program, please don’t hesitate to reach out to us via email: