HR: 1330h
AN: AE22A-1112    [PDF]
TI: GPS Radiosonde with Spread-Spectrum Transmitter for Aerial dE/dt Studies
AU: * Sonnenfeld, R
EM: rsonnenf@nmt.edu
AF: New Mexico Inst Mining \& Tech, Physics Dept., 801 Leroy Place, Socorro, NM 87801 United States
AU: John, B D
EM: jbattles@nmt.edu
AF: New Mexico Inst Mining \& Tech, Physics Dept., 801 Leroy Place, Socorro, NM 87801 United States
AU: William, W P
EM: winn@loon.nmt.edu
AF: New Mexico Inst Mining \& Tech, Physics Dept., 801 Leroy Place, Socorro, NM 87801 United States
AU: Aulich, G
EM: aulich@grosbeak.nmt.edu
AF: New Mexico Inst Mining \& Tech, Physics Dept., 801 Leroy Place, Socorro, NM 87801 United States
AU: Ken, E
EM: keack@nmt.edu
AF: New Mexico Inst Mining \& Tech, Physics Dept., 801 Leroy Place, Socorro, NM 87801 United States
AB: Inexpensive, low-power and reliable telemetry is a continuous struggle for those engaged in developing balloon-borne instruments for atmospheric electric studies. Several custom designs, by NCAR and others, have enabled much useful work in radiosondes. Also, packet radio technology has been used with great success. Easily obtainable packet radios are currently limited to 9600 baud. In search of higher baud rates that integrate well with microprocessor-based data acquisition systems, we have tested a new commercial off-the-shelf spread-spectrum transmitter. The transmitter operates in the 900 MHz industrial, scientific and medical (ISM) band with a transmit power of 100 mW. The transmitter (a Maxstream XC09-019NST) is used with a dedicated receiver, such that the data to be transmitted is fed via RS-232C protocols to the transmitter, and received as a text string via a serial port on the receiver. We did tests at raw baud rates of 9600 and 19200 (roughly 1000-2000 characters/second). Initial range tests required integrating the transmitter with a GPS and sending the NMEA-position-string (National Marine Electronics Assoc.) to a ground-based receiver. In ground-based tests, we repeatedly saw that a clear line-of-sight between transmitter and receiver was required for successful telemetry. The maximum range obtained during ground tests was 15.3 km at 9600 baud. Initial balloon tests results were, as hoped, more encouraging than ground-based tests. The maximum range (ground distance and altitude) of any balloon transmission was 58.0 km in fair-weather with excellent line-of-sight visibility. Our highest altitude transmission was 28.6 km absolute altitude (25.3 km altitude relative to launch point). These numbers were determined from the GPS coordinates transmitted. Antenna alignment and acceptance angle effects were observed in our received data. For these reasons, the full data rate of 19200 baud was only obtained out to 10 km, and then again around 45-58 km. Performance of the system could be improved by spreading packets over a wider range of spectrum, improving the transmit antenna geometry, increasing power, using a more directional receive antenna; or all of the above.
DE: 3304 Atmospheric electricity
DE: 3324 Lightning
DE: 3394 Instruments and techniques
SC: Atmospheric and Space Electricity [AE]
MN: 2003 Fall Meeting