GPS Tracking, Telemetry And Dual Deployment Payload.


  • Part Number (PN): 09131
  • Manufactured by: Altus Metrum
  • Product Specs:
  • Dimensions: 1.0675" X 2.75" X 0.62" tall (27mm X 69.8mm X 15.7mm)
    Weight: 20.1 g (.71 oz.)

    The Telemetrum requires a HAM radio callsign for use in the USA. 

    Please note: This is NO LONGER a Starter Set. If you would like the TeleDongle (Starter Set), battery, or the new TeleBT, please order them separately. TeleMetrum will charge the battery when connected.

5 Units in Stock

This payload contains everything you might ever need in an electronic device. It does dual deployment, tracks the position of the rocket using GPS technology and it transmits all this data back down to the ground where it can be displayed in real time on a computer. A ground station unit is required to receive the relayed data (must be purchased separately).

TeleMetrum Means "Measure Altitude Remotely." But it Does WAY More...

Small SizeThe TeleMetrum payload does much more than tell you where the rocket is (a GPS dog-tracker mounted in a rocket can do that...)

This is the first GPS payload designed specifically for rockets, and not created from off-the-shelf components that are simply spliced together. Because of this, it is smaller, lighter, and has significantly more capability in controlling dual deployment of the rocket's chutes. And all the components are matched together perfectly so things just work without a lot of fuss or electrical interference between components.

Know Where Your Rocket Is At All Times During The Flight
...and how High it Went
...and If the Dual-Deployment Circuits are Working Correctly

Finally, one single small payload gives you all the advanced features you've desired in rocket electronics:

  • GPS Tracking data so you know your rocket's position.
  • Barometric recording altimeter. Barometric pressure sensor good to 45k feet MSL. Allows you to have perfect dual-deployment flights.
  • 1-axis 70-g (+/-) accelerometer: Used to verify the speed of the rocket, should the vehicle exceed Mach 1. This simplifies setting up dual-deployment settings, because you don't have to worry about mach pressure effects fooling the baro sensor.

    The accelerometer also works for "motor characterization." This means you'll be able to verify after the launch that your rocket motor produced as much thrust as you expected. You'll be able to see the actual motor's thrust curve after each launch and compare it to the predicted thrust. This is great for people that make experimental rocket motors; you can fly the motors you make, instead of burning them all on a thrust stand just to get a thrust curve.

    In addition, because of the accelerometer, the payload also knows the rocket's orientation at power-up (nose up, or laying on its side). The TeleMetrum takes advantage of this to make arming of parachute ejection charges safer. With the TeleMetrum, you have the capability of remote arming of rocket on the launch pad (NO other payload can do this!). This means no more risking your neck climbing a wobbly step-ladder or a tall launch towers to turn on your vehicle's electronics just prior to launch. You can do it from the safety of your ground station. This greatly speeds up launch preparations out on the pad, which means your high-power friends will thank you for making the range run faster so they can fly their rockets too.

  • Telemetry transmitter (70cm ham-band transceiver) allows all the flight data to be seen real-time during the mission. The telemetry system sends flight data 10 times per second during ascent, and once per second after apogee. It also transmits an audio tone once every five seconds that is used for tracking purposes on the ground with a directional rocket locator. The range is over 20 miles (Line-of-sight distance. Of course, this depends antenna you connect with the receiver).

  • Dual deployment parachute control - fires two separate ejection charges. The first is fired at apogee. By default, TeleMetrum will fire the main deployment charge at an elevation of 250 meters (about 820 feet) above ground. There is an override command in the software to allow both the apogee and the main chutes to deploy at different altitudes. This "apogee delay" feature is to ensure multiple altimeters don't fire at the same time when you're flying redundant electronics, which is a requirement when flying a Level-3 high-power certification attempt.

  • On-board non-volatile memory (2 MB) for flight data storage records data at 100 samples/second from the barometer and accelerometer, it also captures data at 3 samples/second for battery voltage, temperature and deployment charge continuity. GPS is recorded once per second. With 2MB of memory on-board, it can capture over 40 minutes of flight data. This allows you to download flight data after the mission is over, just in case your telemetry signal drops out. There's actually more data logged (particularly during the ascent phase) than is sent over the telemetry link, so you'll get a huge data cache after you get your rocket back. And you don't even have to remove the payload from the rocket or hook up any wires. After the rocket has landed and you have it sitting on your prep-table, you can simply command it to transmit all its stored flight data to your computer.

  • Funtions as a battery charger (Battery not included). It automatically gets recharged whenever the USB cord (included too) is connected to your computer.

  • Use it as a rocket tracker too. You can use your radio direction finder to home in on the rocket should it land in rough scrub or a forested area.

  • Open-source software allows you to expand the functionality of the product should you wish to add extra features.


Tell Me More About The TeleMetrum Payload

Part 1

(View on YouTube if you cannot see the video above)

Part 2

(View on YouTube if you cannot see the video above)

Part 3

(View on YouTube if you cannot see the video above)

How Do You View The TeleMetrum Flight Data?

Altos UI TeleMetrumTo view your telemetry data that is transmitted by the TeleMetrum, you'll download and install onto your computer the ground station program called "AltosUI" from the Altus Metrum web site.

This java-based software connects you to the TeleMetrum during flight so you can see how many GPS satellites it is receiving data from as well as displaying the current and max values for key parameters during flight. It also logs all the telemetry data to disk for post-processing after the flight.

The software even includes voice synthesis during the flight so that your eyes can stay on the rocket while it speaks to you and tells how high and where downrange it is. Watching the rocket is a lot more fun than staring at a computer screen, wouldn't you agree?

Altos UI TelemetrumThe AltosUI software includes post flight analysis tools that makes it easy to extract usable things like apogee altitude, max acceleration, and max velocity. You can also generate and view a standard set of plots showing the altitude, acceleration, and velocity of the rocket during flight (such as the ones show here to the left).

The program also export the flight data to a standard CSV (comma separated values) file format that can be read in to a spreadsheet program. This allows you to do additional analysis on your flight data.

Plot of an actual rocket launchThe AltosUI program even generates KML files for viewing flights in GoogleEarth (see image to the left)! The data is color-coded so you can see the boost phase, the coast phase, and the descent phase.

The coast phase is distinguished in two parts called "fast coast" and "slow-coast". During fast coast, the rocket's speed is higher than 200 m/s, which tells the TeleMetrum payload that the rocket is going way too fast for safe parachute deployment. It will inhibit the ejection charges during this phase because the rocket would probably shred the chutes if they deployed at this speed.

AltosUI Examples

Launch Pad State
Altos UI Telemetrum

Ascent State
Altos UI Telemetrum

Descent State
Altos UI Telemetrum

Landed State
Altos UI Telemetrum

Site map
Altos UI Telemetrum

How Does Dual Deployment Work?

The TeleMetrum payload works by sensing the altitude of the rocket. In simple terms, it is an altimeter. But this one is different, it has three sensors and a sophisticated brain and extra hook-ups to to send electricity to two different ejection charges.

As the rocket takes off, this electronic payload is calculating the altitude of the rocket. When it senses the peak altitude, called apogee, it sends electricity to one of the starters. This starter sets off a small charge of black powder. That pressurizes one section of the rocket and spits out the small parachute (called a drogue chute).

While the drogue chute brings down the rocket quickly, the payload is still sensing the altitude of the rocket. When it descends to a pre-programmed height (which you can control), it then triggers a second time. This time is ignites another black powder ejection charge which pushes out the main parachute. Since the rocket is now closer to the ground, the wind really doesn't have the time to push it downrange too far. So it lands slowly, but much closer to the launch pad. That means you don't have to walk very far to retrieve your rocket.

Single vs. Dual Deployment

My Personal Experience Using The TeleMetrum - By Tim Van Milligan
Loading the Apogee Fireball on the padFor the NARAM launch here in Colorado in August 2010, I decided that I'd go for my Level 2 high-power certification. For this, most people would choose to be conservative and use single-deployment of the parachute in order to minimize the complexity of the rocket. And I started that way too.

I built a big rocket based around the 5.5-inch diameter Blue-Tube airframe tube with a LOC 5.5" nose cone. Other features included a 38mm motor mount with a Cesaroni J285 reloadable rocket motor. I also choose a 52 inch diameter SkyAngle parachute to bring the rocket back down to the ground. To hold the motor in, I used the 38mm Aero Pack motor retainer. It was a stout rocket that I was sure would survive the flight.


Tele-Metrum on the E-bay sledBut when we got the TeleMetrum payload in from the Altus Metrum company, I was so impressed that I decided to modify the rocket to use dual deployment. It was an easy modification, as all I had to do was cut the main tube in half and insert an Always Ready Rocketry 5.5" Electronics Bay and an extra length of 1500# Kevlar for the shock cord and an additional Heat Shield parachute protector.

The electronics bay was more than adequate to mount the TeleMetrum payload. In fact, even the 7-inch long antenna on the TeleMetrum fit on the plywood sled inside the electronics-bay.

Close-up of the altimeter mounting systemI did have a little bit of help mounting the TeleMetrum board in the rocket. Bdale Garbee of Altus Metrum came by my workshop and helped me mount the board to the plywood sled and gave me some great tips for running the wires around the board.

As you can see in the photo to the right, the layout is rather clean and straight forward. The red and black wires run to a push-switch to turn the unit on and off, and the green wires run to the forward ejection charge starter. The battery is smaller than the TeleMetrum and was mounted on the back-side of the plywood sled. The only thing not shown in the photo is the third set of wires that go to the rear ejection charge starter.


Lift off of the Apogee FireballOn launch day, I got telemetry help from Bob Finch, who was the first customer to purchase the TeleMetrum from Altus Metrum. Bob knows much more about the computer aspects of the TeleMetrum than I do, and he is also a licensed Ham radio operator. Really, all I had to do was turn on the TeleMetrum when the rocket was brought out to the pad. Bob then checked the radio link from his computer to my TeleMetrum and we were ready for launch.

The TeleMetrum is already pre-set for dual deployment capability, so our radio connection was only to download the flight data.

I had some butterflies in my stomach, like all fliers get when they go through a certification attempt. I tried to video-tape the launch, but my hands were so shaky that I couldn't keep the camera focused on the flight. So all I got were these great flight photos taken by other onlookers to the launch.

Dual-Deployment chuteSince it was a big and heavy rocket, the actual flight didn't go all that high, only a bit over 1,600 feet. It happened fast in real-time, but for me it seemed to take forever. The rocket lumbered off the pad and weathercocked right into the slight breeze. So it was arching heavily when it reached its apogee point.

The TeleMetrum didn't care. It sensed apogee and kicked out the small drogue parachute right at the top. Less than 30 seconds later, as the rocket was descending, the TeleMetrum fired off the starter for the ejection charge that popped out the 52" diameter SkyAngle parachute. When it blossomed open, I could hear an eruption of applause from the crowd of spectators. They all love to see a great dual-deployment flight, as the extra suspense of waiting for the 2nd chute always grabs their attention. But with the TeleMetrum payload, it was almost a forgone conclusion.

And while the flight wasn't all that high, we got reams of flight data back via telemetry. Cool!


Remote Ejection Charge Test Using The TeleMetrum

One of the neat features of the TeleMetrum is that it makes performing ejection charge testing on the ground a lot easier because it can be done via remote control. In other words, you don't have to run extra wires to the rocket to set off the ejection charges. In the video shown below, you'll see a quick-and-dirty ejection charge test on a high power rocket.

(View on YouTube if you cannot see the video above)

Why perform an ejection charge test?

The main reason is to make sure you have enough black-powder in the ejection charge to separate the rocket and kick out the parachute. A lot of high power rockets use shear pins to hold the rocket together to prevent pre-mature separation while the rocket is still ascending. The ejection charge must be strong enough to break those pins when it is time for the parachute to pop out.

Performing this test also verifies that your electronics is configured properly.

Frequently Asked Questions about the TeleMetrum GPS Payload:

Q. Where can I download the Instruction Manual?

A. Download it from the Altus Metrum Web site.

Q. Where do I get a HAM radio "Technician Class License" so I can use this product?

A. It is not hard. If non-rocketry people can get licensed, so can you. You're a rocket scientist, right? Start here:

Q. Why is a HAM radio license required?

A. While some competing products claim they do not require a license, they do not have the features of the TeleMetrum. These other GPS transmitters are made from off-the-shelf components, and all they do is tell you the position of the rocket based on GPS satellites. That is all they are licensed for by the Federal Communications Commission (FCC). Once you start transmitting more data, like the TeleMetrum does, the FCC requires {Part 15 of the FCC regulations} that the entire device (the complete radio system and the antenna) needs to be re-certified to make sure they are not radiating too much power and leaking out of their assigned frequency. Or... you need to have a HAM license to use them.

To be honest, the guys at Altus Metrum wish they could get it certified to use without a HAM license. It probably could pass easily. But the certification fee is over $20,000. When you're talking that amount of money, it is hard to justify that amount of investment in a small hobby like rocketry.

The other products simply do not have the same data transmitting capability as the TeleMetrum. And if they claim they do, it might be a good idea to check to see if their products have actually been tested and certified by the FCC.

Q. What is the range of the TeleMetrum system?

A. There are 4 variables that determine the maximum range of the telemetry system. Those are the transmit power output, the transmit antenna gain, the receive antenna gain, and the receiver sensitivity. Improving any one of the four will give greater range. The easiest one to make better is the receive antenna gain.

The theoretical maximum range for the system with a 3-element yagi antenna on the ground is about 50km (or 30 miles). However, there are a number of sources of loss that are hard to model that conspire to make the *actual* range something less than the theoretical range. Tests performed at Altus Metrum have shown that a 3-element yagi antenna yields good telemetry from rockets to 20 Km (65,600 feet) altitude, and that a 11-element yagi antenna can receive telemetry from the TeleMetrum to around 100 Km (62 miles). Finally, the software reports the signal strength, so it's pretty easy for someone to "ground test" the range of the system in a given airframe before they fly it.

Q. How long can the TeleMetrum sit in idle mode prior to launch with the 850/900mAh battery (not included)?

A. The TeleMetrum turns down the radio so that it's only transmitting once per second on the pad prior to detecting launch. During this time, it draws something like 60-80mA of power. With the 900mAh battery, that's somewhere more than 10 hours of run time.

Of course, the TeleMetrum is also transmitting the battery voltage too. So you'll be confident that everything will work before the motor ignites, because you'll be able to check on the status of your battery while you're waiting on the other flyers to get their butts in gear so you can launch your rocket.

Q. How long will the 850/900mAh battery last before dead? I'm planning on using it in a High Altitude Balloon project I'm running.

A. The maximum power consumed by the electronics is less than 150mA, so even using as much power as possible, the battery should last for 6 hours. The system doesn't use maximum power all of the time though, telemetry packets take about 50ms each, and once the GPS chip is locked, it uses less than half its maximum power.

The capacity of the battery will be affected by temperature, so at altitude you might see significantly lower battery capacity. A bit of testing in a local freezer might demonstrate the effective working capacity of the battery under worst-cast conditions.

In regards to memory for data storage, please remember that the regular TeleMega firmware is designed for rocket flights. It reports ascent telemetry data at 10Hz, records ascent readings to flash at 100Hz. These are both possibly faster than you'd like and will use up more of the memory. At 100Hz, even at the largest possible flight storage, you'll consume the flash storage in about 40 minutes.

If you know someone with experience in microcontrollers, you might consider changing the firmware to be more 'balloon friendly', recording and reporting data at a lower rate through the whole flight. All of the source code for the firmware is available on the web site, and the sdcc compiler is available from

Get the custom firmware for balloon flights from: 

Q. Do you sell any type of ejection charges that could be used with the device on this page?

A. No. The ejection charge is always made from loose black powder. Because black powder is regulated by the government, you have to purchase it from a gun store (one that specializes in muzzle-loading supplies). You also need to be at least 18 years old to use loose black powder in this manner.

Q. Does it matter what elevation the launch field is?

A. The altimeter samples the air on the ground, so it knows the altitude of the ground level. So when you set it to deploy the main chute at 500 feet, it will know that is above ground level. It doesn't matter where you start.

Q. What is the TeleMetrum's launch detect trigger?

A. With the TeleMetrum, the "launch detect" trigger can be either a 20 meter increase in altitude OR the combination of acceleration greater than 2g with a velocity greater than 5 meters/second as launch. The velocity number is calculated from accel data. This approach is an effective way of preventing a single "bump" of acceleration from causing a false launch detection.

Q. Will this device trigger (detect a luanch) if the rocket is aimed horizontally instead of vertically?

A. No. It is only designed to detect launch from avertical position, furthermore, it will only go into 'flight' mode when
boosted in a vertical orientation. However, the manufacturer says that they've had some customers modify the stock firmware (it is open-source firmware). If you have access to any embedded firmware developers, changing the firmware to do what you need can be accomplished. Apogee Components does not have this capability, nor do we know anyone that does. You're on your own with this modification to the firmware.

Q. What if I want to use a Pyro battery in addition? Where do I connect it?

A. If you plan on using a separate pyro battery in addition to the LiPo battery, the TeleMetrum board needs a special jumper wire attached. This requires the board be returned to the manufacturer for modification."

Q. Does the TeleMetrum work with Hybrid-Propellant rocket engines which vibrate the rocket at high frequencies?

A. It should work just fine. The TeleMetrum use the accelerometer to detect high speed flight, but not for apogee detection. The unit integrates the accelerometer output to find velocity; when that value is >200m/s, it ignores any barometric readings that might indicate apogee.  Apogee-detection is done purely with the barometric sensor which does not suffer from systematic errors due to vibration. The TeleMetrum has been tested in a shake-table mounted inside a vacuum chamber to characterize the amount of noise that introduces so that it could correctly compensate for for hybrid propellant motors.

Q. Does the TeleMetrum work in Hybrid Rockets?

A. Yes. Here is a link to a video of Hybrid rocket that used the Telemetrum.  The page is in Italian, please click here for a Google Translation into English. 


Modern High Power RocketryQ. How easy is it to set up dual-deployment?

A. To be honest, it is not a beginner-level operation. For starters, you have to design your rocket with two separate parachute compartments. This is detailed extensively in the book Modern High Power Rocketry 2. We highly recommend this book if you are new to large rocket or dual deployment techniques.





G-Wiz Flight ComputersQ. How does this electronic gizmo compare to other dual-deployment devices?

A. This device uses a barometric sensor, and accelerometer, and GPS receiver to determine how high the rocket is. If you don't need the GPS receiver, then the G-Wiz Flight Computer may be sufficient for your complex project. 


Videos and Tips on Dual Deployment

What is dual deployment? Why would you use it? What kind of equipment do you need? Long-time friend and patron of Apogee Components, Jeff Lane, joins Tim in a series of videos answering these questions on using the Entacore AIM-USB altimeter in your next high power project. While this series directly pertains to the Entacore AIM altimeter, the knowledge is easily translateable to the other dual-deployment altimeters sold by Apogee Components.

Reviews for the TeleMetrum

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