Telemetry - Ground Station

Ground stations are one of two main components of our telemetry system.

The second one are the Telemetry - Transmitter.

Device Description

At the operation of free flying measuring probes, the scientist always faces the same question:
How do I get the measured data of my system?

There are two solutions:

1. On-board - data storage and recovering after touchdown

Pro's:

  • simple
  • reliable, no data losses as long as the recovery operation is successful

Con's:

  • complete data loss, when the recovery fails
  • no direct control or monitoring of the probes status and trajectory

2. Live - data transmission over telemetry

Pro's:

  • live - data monitoring and analyzation possible
  • command uplink allows direct user response on situation changes and direct control of the probe
  • a successful recovery operation is not necessary to get the measured data
  • this system allows One-Way-Flights, wherein no recovery is planned at all, for example a flight to the open sea

Con's:

  • higher technical effort on board and on the ground

Our ground stations, together with our transmitters, form a closed data transmission system. The communication is done over a coded radio network, so only our ground stations are able to work with our transmitters and vice versa. To reduce the technical effort for the user these two main components are available as complete packages, which contain all necessary parts and functions to operate a probe with this telemetry.

Features:

  • very mobile, simple controls despite of its large scope of functions:

    • transport: 1 car (Audi A3 or bigger)
    • setup: 1-2 persons
    • operation: 1 person
  • independent of any local infrastructure (energy supply over generators, battery packs or the supplied power supply)
  • high weather resistance
  • robust steel tripod
  • antenna rotor for rotation and inclination
  • integrated automatic antenna tracking and alignment function
  • high gain directional antenna and long rang
  • support of multiple ground stations, this way any range can be reached
  • downlink for user data and status information
  • uplink for control commands, direct control of the transmitter and the connected devices
  • high transmission reliability (packet loss rate < 1%, despite of frequently connection losses of several minutes)
  • live data transmission
  • integrated GPS
  • SD-card for logs of the systems functionality and the whole radio traffic (even without a connected PC)
  • PC-Program with user interface for system control, monitoring and data log
  • when used with research balloons: trajectory and landing area forecast, including live update during the flight
  • robust wood cases for transport

Expansion options:

  • 7 free programmable digital/analog input/output - pins for control and measurement tasks (planned)
  • second radio channel for higher transmission capacity (planned)

The system has additional unused resources, like internal hardware interfaces, which are reserved for future expansions.

If you have special wishes, don't hesitate to contact us! We are willing to discuss about additional functions any time.

Technical Details

electronics
 
input voltage range 10 - 22 V DC
max. power consumption 6 W
temperature range -40 - +85 °C
supplied power supply
 
output voltage 13.8 V
max. output current 20 A
max. power 275 W
input voltage range 100 - 110 V / 220 - 240 V AC, 50 - 60 Hz
dimensions 154 x 102 x 53 mm
communication
 
digital interfaces 2 (1x system control, 1x user data stream)
interface types

optional

currently: USB, RS232, RS422, RS485 (planned: CAN, LAN)

baud rates up to 512 kBaud
radio - frequency band standard: 869 MHz (optional: 920 MHz, 2.4 GHz, 3.4 GHz)
radio - output power up to 1 W
radio - data rate 160 kBaud
radio - range

over 100 km (at 869 - 920 MHz)

over 50 km (at 2.4 - 3.4 GHz)

radio - antenna options 2 m, 2.5 m or 3 m grid parabolic dish (at 869 MHz)
antenna rotor
 
type rotation + inclination (azimuth + elevation)
adjustment speed  
control / tracking manual or automatic by GPS
max. power consumption 275 W
packaging und transport
 
3 robust wood cases each < 50 kg

Application

Our ground stations, or the entire telemetry system, was designed to operate where large among of data have to be transferred between two places over a long distance, but no local infrastructure is available or not intended to be used. A concrete example are measurement systems on board of free flying research balloons, which measured data have to be transferred to the user on the ground directly.

These balloons fly at altitudes of over 30 km and mostly over inaccessible areas, like mountains or oceans. So there is no possibility to fall back on mobile networks for example. Satellite based solutions are conceivable, but their data transmission rates can suffer from dynamic fluctuations (from band width redistributions by the provider).
In contrast to that, our system provides a direct data link in both directions (up- und downlink) with a transmission delay of just a few 100 msec.

For the operation of our system, some requirements have to be fulfilled:

  • for the radio connection a direct sight line is essential
  • it's necessary to check with the national institute for frequency usage rights, under which conditions this radio system (frequency, transmission power, ...) is allowed to be operated

The following describes some typical operation scenarios (see also the application part of our transmitters):

1. Simple flight of a research balloon with recovery after touchdown

Situation: research flight with balloon and recovery of the measurement instrument afterwards.
  • In the simplest way the ground station is set up near the launch area of the balloon. Thanks to the integrated automatic tracking the antenna always faces the transmitter's exact position. This way we achieve a range of over 100 km.
  • The trajectory and the landing area can be calculated by the forecast program and updated by the live measured data during the flight. So, the recovery team can be guided near the probable landing point, which saves time and money.
  • If a range of 100 km is not enough, then the trajectory forecast also allows to position the ground station along this flight path in 50 - 100 km distance to the launch area. This way the flight range can be nearly doubled.
  • Because of the live data transfer to the ground station, it's not catastrophic, if the recovery fails (for example: loss of the system after a water landing). The data are already secure.
  • Through the uplink both, the transmitters and the connected measurement systems, behaviour can be influenced during the flight. For example you could change the sample rate of the sensors as soon as the balloon enters a very interesting zone. Theoretically the carrier system itself (not necessarily a balloon) could be remotely controlled.

2. Flight of a research balloon with selective landing and recovery

Situation: research flight with balloon and recovery of the measurement instrument afterwards. The landing point forecast is located in an area with large expanse of water, like if the balloon fly's from land in direction of an ocean.
  • In this case you can equip the measurement system with a cutter, which can be remote controlled and separates the instrument from the balloon, so that the flight can be interrupted any time.
  • During the flight the PC-program calculates live updates for the landing point forecast from the transmitted data. But this program does not only calculate the regular landing area, but also the landing area from the current position, if the balloon would be cut immediately.
  • Thanks to our uplink, the cutter can be selectively triggered as soon as the current landing point forecast is located in a favourable area. In our case of a flight in direction to an ocean, we could send the cut command as soon as the landing forecast points shortly before the coast line to allow recovery ashore.

3. One-way flight of a research balloon without recovery

Situation: research flight with balloon, launched at the coast line and flight direction to the open sea.
  • Without a live telemetry such a flight would cause an extremely high effort for the recovery.
  • With our telemetry a recovery operation is not necessary, because the data are already secure in the ground station, which saves time and money.
  • Additionally the forecast program can be used to obtain the optimal launch time in terms of wind direction and strength.

4. Long range flight

Situation: research flight with balloon, wherein the trajectory forecast shows a much longer flight distance than the max. range of a telemetry station
  • The telemetry system is designed to support multiple ground stations
  • For that the trajectory forecast from our PC-program is an essential requirement
  • Then, ground station 1 will be located at the launch area (with about 100 km range)
  • A mobile team will set up a 2. ground station along the calculated flight path in, for example, 150 km distance to the launch point (also has about 100 km range). This way the radio areas of both stations overlap each other by at least 50 km.
  • Now, when the balloon leaves the area of station 1 and the signal is getting weaker, team 1 hands the balloons GPS position over to the 2. team. The automatic alignment function rotates the antenna of station 2 exactly to the balloons position. As soon as the transmitters signal is received with proper strength, also the automatic tracking will be activated and so also the user stream reception and transmitter controls can be handed over to station 2.
  • This way already with only 2 ground stations a flight range of 250 - 300 km is possible
  • The number of ground stations, which can be combined in such a way, is not limited. So theoretical, with enough stations, any flight distance could be monitored.

5. Network of ground stations

Situation: During a long time campaign a big number of research flights should be started from a fix launch area, wherein the trajectories can vary widely
  • The operation with multiple ground stations is not limited to a line along one flight path.
  • They also can be installed in a grid around the launch area.
  • This way every possible trajectory is covered, you just have to hand over the control to the nearest station (or the one with the best signal quality).

6. Other applications

The telemetry system features standardised interfaces for data exchange, controls, supply and antennas, so it's potentially usable in other fields of application also.

  • Data connection to scientific buoys on the sea
    A ground station in a slightly elevated position, on one hand could establish a permanent connection to 1 buoy, or on the other hand could switch periodically between several buoys. In the latter case, the antenna alignment to the different targets can be left to the automatic controls, as long as the GPS positions of the buoys are known.

Cooperation

This development was done in cooperation with the Leibniz-Institute of Atmospheric Physics e.V. at the University Rostock (IAP).

This development was financially supported by the Federal Ministry of Economy and Energy following a decision of the German Federal Parliament.