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TEPES [tepesh] is a high altitude balloon project consisting of several missions that have different goals. One type of mission will focus on long distance flight: small balloons with minimalistic payloads intended to fly for long periods of time and travel tens of thousands of kilometers through Earth's atmosphere. These pico balloons (designated V-TEPES) are not meant to be recovered. Once they stop transmitting their data (due to any kind of failure, e.g. fried electronics, permanent power loss, bursting) they are lost forever. Other missions will focus on collecting a broader spectrum of atmospheric parameters, as well as taking pictures, storing most of them internally and sending some via SSTV. These balloons (designated D-TEPES) are larger and carry a bulkier payload that needs to be recovered in order for the mission to be considered a success.

Tracking will (most likely) be done via APRS, enabling anyone connected to the internet to follow the status of the misson in real time - balloon's position, altitude, speed and some other parameters. Also, those interested (and in range) can tune in, receive and decode SSTV images. Launch dates, sites, callsigns and frequencies will be announced at a later date.

PAYLOADS:

- Pico Balloons will carry GPS and radio equipment for APRS tracking, basic sensors (temperature and humidity) and some type of powersource (be it a battery or a combination between solar cells and batteries). Due to their small size these pico balloons provide limited lift, so the total weight must be kept to a minimum (around 100g).

- Meteorological Balloons will lift payloads of 200 grams and heavier up to an altitude of 30,000 meters or more. As the balloon rises, it reaches less dense air (the atmospheric pressure is lower at higher altitudes) which causes the gas trapped inside to expand. A balloon will eventually burst due to overinflation. The descent rate will be controlled by a parachute deployed after burst. These balloons will carry GPS for tracking purposes, record data from multiple sensors and take photos, as well as transmit SSTV, telemetry and morse code messages to listeners at pre-determined time intervals. A ground team must chase the balloon at all times to facilitate the recovery of its payload. In the event that the balloon drifts near any of the borders, a deliberate burst is initiated for early payload recovery.

The electronics are based on Arduino or Pi Zero (for V missions) and Raspberry Pi (for D missions). This might change, as the systems are still in the early stages of development. Radio communication equipment, sensors and different modules will be added progressively, while keeping a close eye on power requirements and weight budget.

BALLOONS & GAS:

The V-type balloons are small party balloons made of Qualatex. The D-type balloons are made of latex and their weight alone is around 100 grams and above (large, 3 kilogram balloons also exist). The smallest balloons we'll probably use for the D-TEPES missions are 350 grams. Lift is achieved by filling the balloons with Helium gas. Roughly one cubic meter of Helium is required for each kilogram to be lifted.

RECOVERY:

In the case of D missions, balloon bursting will cause the payload to fall back to ground. The return flight is slowed down by parachute to preserve payload integrity.