GPSonde M2K2 (WMO Code 56) Patrick CHARPENTIER - Rémy PEPIN MODEM - France ET-UASI Geneva – March 2004

Design M2K2 GPSonde (WMO code : 56) is an updated version of the former GL98 GPSonde. The technology is similar as well and M2K2 design has been conducted in accordance with the following guide lines : Research of technical solutions allowing cost reduction  Optimization of electronic design  Reduction of power consomption (4 dry-cells instead of 8)  Reduction of size and weight Improvement of general performances  More powerfull microprocessor  3 entries for connection of additionnal sensors without interface  Optional buit-in pressure sensor Avoid any fundamenal change in respect to T and U sensors  New design of sensor boom to prevent eventualdamage during handling

General features M2K2 GPSonde hold on general specifications from previous GL98 :  3D GPS board: Position with latitude, longitude et altitude  Transmitter: MHz synthetizer Digital data transmission Narrow bandwidth Max drift ±2 KHz 200 KHz step frequency setting  Power supply: 4 dry cells : Autonomy > 3 h  Factory calibration: Stored on EEPROM

New specifications Physical features  Weight: 210g  Dimensions: 92 x 107 x 160 mm Electronics optimization  All functionalities (Transmitter, GPS, microprocessor…) are implemented on an unique electronic board High performance microprocessor  Reprogrammable,  3 entries for additional sensors (Ozone, Snow-White,…). No interface needed for connection  Noise reduction on temperature measurements

New generation 3D GPS board  Short initialization time Power supply  Significative reduction of energy comsomption  4-battery pack Optional pressure sensor  On standard version, pressure is calculated from GPS altitude. M2K2-P version is delivered with a pressure transducer. In this case, both calculated and measured pressures will be available.

New boom design The new boom has an additonnal end leg in order to better preserve the balloon in case of impact with it. (New design is presented on the left side).

T emperature sensor Temperature sensor consists in a thermistor chip wrapped into a glass ball. Its tiny size (0,9 x 2 mm) allows excellent response time around 1 to 1,3 sec. Temperature sensor is led on a layer processed against humidity and solar radiations. Boom end is painted with a special white coating to reduce solar radiation effects.

Temperature sensor details

Humidity sensor Humidity sensor consists in a capacitor of which value is directly proportional to relative humidity. It is composed of 3 primary components :  Basic layer as an electrode  A dielectric of which characteristics vary along relative humidity  A short response porous electrode as the second electrode of the capacitor n A cap is protecting the sensor from rain and mechanical damage

Humidity sensor improvement Humidity sensor size is larger in order to improve response time. Former sensor was connected to the boom through a thin thread. In order to reduce risk of dammage, sensor is now fitted like a surface mounted component with a metallic hole in its center.

Original dual-face concept Hight accuracy High Haute reliability Tiny sensor 0% to 100% range Short response

Sensor specifications TEMPERATURE HUMIDITY Sensor type: Thermistance !Capacité Measurement range: +50° to –90° !0% to 100% Resolution: 0.1°C !0.1% Absolute accuracy: +/- 0.5°C !+/-5% Response time: <2s !<2s Measurement rate: 1 Hz ! 1 Hz Factory calibration: Stored on EPROM Calibration prior launch: Ground check system

GPS specifications GPS WINDFINDING General: DGPS with unlimited altitude - C/A Position accuracy: 10 m Horiz. speed accuracy: 0.15 m/s Wind dir. accuracy: 2 ° Position: 0.01 m Horiz. speed resolution: 0.01 m/s Direction resolution : 0.1 ° Measurement rate: 1 Hz PRESSURE Range : 1050 to 3 hPa Accuracy: ±2 hPa at 1050 hPa; ±0.5 hPa at 10 hPa Resolution: 1 hPa at 1050 hPa; 0.1 hPa at 20hPa