SPRITES DETECTION

This flight was part of the Sprites 99 Balloon Campaign, conducted by the University of Houston's Space Physics Group, aimed to investigate transient luminous events (TLEs) such as red sprites, blue jets, elves, and anomalous optical events (AOEs) occurring in the mesosphere and ionosphere above thunderstorms.

Each balloon carried a comprehensive suite of instruments designed to investigate transient luminous events and their associated electromagnetic phenomena from the stratosphere. The payload, weighing approximately 100 kg, was launched via high-altitude balloons to altitudes exceeding 35 km, positioning it optimally for observing sprites above mesoscale convective systems.

Central to the instrumentation were two three-axis electric field detectors. One was a high-gain, low-voltage system with dynamic ranges of ±5 V/m and ±2 V/m, while the other was a low-gain, high-voltage system capable of measuring up to ±100 V/m. These detectors, developed by the Space Physics Group at the University of Houston, featured preamplifiers with high dynamic range, slew rate, and input impedance, enabling precise vector measurements of electric fields in the stratosphere. The data acquisition system employed multiple telemetry approaches: real-time analog waveform transmission at 4 kHz bandwidth, a 1 kHz sample rate pulse code modulated (PCM) telemetry link, and an event-triggered system capturing bursts at 50 kHz sampling rate, storing data onboard for post-flight analysis.

To complement the electric field measurements, the payload included magnetic field sensors comprising three-axis induction or search coil magnetometers with bandwidths up to 100 kHz. These instruments facilitated the analysis of extremely low frequency (ELF) magnetic signatures associated with sprite activity, aiding in the estimation of current magnitudes involved in such events.

Atmospheric conductivity was monitored using methods such as the relaxation technique and a version of the blunt probe method, measuring ion conductivity at four-minute intervals. This allowed for the detection of large-scale conductivity changes in the stratosphere, even though direct traversal through a sprite was unlikely.

An air-Earth current sensor, adapted from previous measurements conducted at the South Pole station, was integrated into the payload. This enabled simultaneous measurement of all three terms in Ohm's Law, providing a comprehensive understanding of the electrical environment above thunderstorms.

To detect high-energy phenomena, the payload was equipped with a sodium iodide (NaI) scintillation counter featuring a 125 mm diameter crystal and a 16-channel pulse height analyzer, sensitive to X-rays in the 25 to 250 keV range. Data from this instrument were transmitted every 100 milliseconds, with higher sampling rates stored onboard following event triggers. Additional particle detectors, including a Geiger-Müller tube and two solid-state MeV electron counters, were included to investigate in situ acceleration processes, although the ambient pressure at balloon altitudes limited the detection of low-energy electrons responsible for sprite emissions.

Optical observations were facilitated by two broadband, rapid-response all-sky photometers, which served both as event triggers for high-speed data recording and as monitors of the temporal relationship between tropospheric lightning and sprite emissions.

Navigation and precise timing were achieved through an onboard GPS receiver, ensuring accurate positioning and time-stamping of the collected data. The entire suite of instruments was managed by an onboard computer system that controlled sampling sequences, generated PCM telemetry, and handled high-speed digitization and storage of broadband data during sprite events.

Balloon launched on: 7/6/1999 at 1:14 utc
Launch site: Columbia Scientific Balloon Facility, Palestine, Texas, US  
Balloon launched by: National Scientific Balloon Facility (NSBF)
Balloon manufacturer/size/composition: Zero Pressure Balloon 1.500.000 cuft - SF3-1.507-.8/0-NHR
Balloon serial number: R1.507-0-03
Flight identification number: 1567P
End of flight (L for landing time, W for last contact, otherwise termination time): 7/6/1999 at 9:45 utc
Balloon flight duration (F: time at float only, otherwise total flight time in d:days / h:hours or m:minutes - ): F 6 h 33 m
Landing site: 5 miles W of Knickobacker, Texas, US
Campaign: SPRITES 99  

The flight was launched from Palestine, Texas at 1:14 UTC on July 6th, 1999 reaching the float altitude at 3:13 UTC.

After a flight of near 8 hours cutdown command was transmited at 9:45 UTC on the same day.

Flight Performance of all systems was nominal.

This was a engineering flight test before a campaign that involved another two launches.

• Ground and Balloon-Borne Observations of Sprites and Jets University of Houston Website
• Statistics and properties of transient luminous events found in the 1999 Sprites Balloon Campaign Advances in Space Research 34 (2004) 1811