GPSonde M2K2 (WMO Code 56)

Patrick CHARPENTIER - Rémy PEPIN

MODEM - France

ET-UASI

Geneva – 17-20 March 2004

DesignM2K2 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 featuresM2K2 GPSonde hold on general specifications from previous GL98 : 3D GPS board : Position with latitude, longitude et altitude

Transmitter : 400-406 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).

Temperature 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 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

P I S S

Sensor specificationsTEMPERATURE 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 specificationsGPS WINDFINDING

General : DGPS with unlimited altitude - C/APosition accuracy: 10 mHoriz. speed accuracy : 0.15 m/sWind dir. accuracy : 2 °Position : 0.01 mHoriz. speed resolution : 0.01 m/sDirection resolution : 0.1 °Measurement rate : 1 Hz

PRESSURERange : 1050 to 3 hPaAccuracy : ±2 hPa at 1050 hPa; ±0.5 hPa at 10 hPa

Resolution : 1 hPa at 1050 hPa; 0.1 hPa at 20hPa