SkyMet - Drone Meteorology

Overview:

Discarded weather balloons and radiosonde equipment can be hazardous to wildlife and the environment. We will use a quadcopter/drone as a reusable vehicle for the radiosonde equipment while taking meteorological data.

We will build a platform to carry an iMet-4 radiosonde on the Hovergames quadcopter, and interface the telemetry to extract the required data.

Our solution will use the drone to replace the rubber weather balloon thus making the system reusable and non-polluting.

The Drone Kit:

The NXP KIT-HGDRONEK66 with updated motors.

The kit came with everything you need to assemble the drone including a small set of screwdriver tools.

https://nxp.gitbook.io/hovergames/userguide/getting-started/drone-kit-contents

The starting page for all the HoverGames II information can be found at the following link:

https://nxp.gitbook.io/hovergames/

I did have to order a few LiPo batteries. A few hours later, and a new drone was born. There are some helpful assembly videos on the internet.

https://nxp.gitbook.io/hovergames/userguide/assembly

The RDDRONE-FMUK66 was programmed with the PX4 software using the given programming tools and watching the installation videos.

I designed a small box for the 3D printer to hold the Adafruit BME688 board on the quadcopter, and published it on Thingiverse.

https://www.thingiverse.com/thing:5722287

The Radiosonde:

The meteorological data will come from an InterMet Systems iMet-4 Radiosonde.

InterMet now has a radiosonde specifically targeted to a UAS called iMet-XQ2, however, there were none available for this project.

iMet-XQ2 UAV Sensor

https://www.intermetsystems.com/products/imet-xq2-uav-sensor/

https://www.intermetsystems.com/wp-content/uploads/2022/01/iMet-XQ2-droneMount-1024x767.jpg

https://www.intermetsystems.com/wp-content/uploads/2022/01/202021_iMet-XQ2_210415.pdf

https://www.intermetsystems.com/wp-content/uploads/2022/01/202084-12_iMet-4_Technical_Data_Sheet.pdf

• The iMet-4 measures air temperature with a small glass bead thermistor.
• The humidity sensor is a thin-film capacitive polymer that responds directly to relative humidity
• The iMet-4 is equipped with a pressure sensor to calculate height at lower levels in the atmosphere. Once the radiosonde reaches an optimal height, pressure is derived using GPS altitude combined with temperature and humidity data
• Data from the radiosonde's GPS receiver is used to calculate wind speed and direction, This data will be affected by being on a quadcopter rather than a balloon.
• The iMet-4 radiosonde can transmit to an effective range of over 250 km using 403 MHz
• The telemetry uses AFSK encoding at 1200 baud

I found several software packages to decode the iMet-4 data, iMetOS-II, NOAA’s SkySonde, SondeMonitor and En-Sci’s DAS-2 Software.

https://www.intermetsystems.com/

https://www.esrl.noaa.gov/gmd/ozwv/wvap/sw.html

https://www.en-sci.com/ecc-ozonesonde/

ftp://ftp.cmdl.noaa.gov/user/emrys/SkySonde%20User%20Manual.pdf

https://sondemonitor.software.informer.com/5.5/

I replaced the soldered-in batteries with battery sockets for the CR123A batteries so that they can be replaced easily. If I can find rechargeable batteries that will even be better.

The SoundMonitor software had difficulty recognizing my radio receiver USB input.

Another software option is DireWolf with RTL-SDR for a Linux environment such as Raspberry Pi.

We recently sent up a meteorological balloon and used the Intermet iMetOS-II software for data logging.

The first problem I ran into was the iMetOS-II software assumes you are using a balloon and plots values against altitude and not vs. time, so you can't take benchtop data with a realtime graph.

Results:

Using the SkySonde client and server I managed to take some radiosonde data and plot it against time. Humidity, pressure, and temperature data were good, but altitude, wind speed, and direction data were not so good. A sensor pack designed for deployment on a UAS should be designed with its limitations and features maximized for the characteristics of a UAS flight. Wind speed and direction could be obtained with an ultrasonic anemometer located outside of the propeller wash area lowered by a small winch, or positioned above the vehicle. An interface to the NavQ+ from the sensor pack for direct telemetry would be the next good feature to add to the system.

Summary:

Replacing a weather balloon with a quadcopter drone poses some unique challenges. A weather balloon can travel 20km in altitude and hundreds of km away from the starting position before landing. The current laws for drone flying is to keep the UAS within visual range at all times, to a maximum of 400ft and no flying over people or at night without special permits from the FAA in the USA. The data from a radiosonde on a balloon uses GPS location and altitude via pressure to compute wind velocity. Wind velocity measurement on a quadcopter is difficult due to proximity to propeller flow and no linkage to GPS data as an indicator of wind direction. Reusability of the radiosonde is a nice feature of a drone deployment, however, a serious crash may also destroy the radiosonde.

Another point to make is that an unprotected drone will be damaged if flown in the rain, snow, or other severe weather, while the balloon is not effected so much with weather hazards.

Future Work:

Integrating the BOSCH BME688 sensor to the radiosonde data stream and adding all the telemetry to the drone data stream would be the next part of this project. In addition, programming the drone for a "Standard" flight pattern for the best comparison to an actual balloon flight vs a drone flight using the NavQ+ via ROS.