1. PACER GAP Science Report May 22, 2008 Herman Neal, Mozella Bell, Matthew Ware

2. Science Background The payload ascended through the troposphere, the tropopause, and into the stratosphere to the upper boundary of the ozone maximum. The payload ascended through the troposphere, the tropopause, and into the stratosphere to the upper boundary of the ozone maximum. This figure represents a typical temperature profile of the layers of the atmosphere. However, the specific profile depends on location, particularly the latitude. There is also a seasonal variation with the tropopause at higher altitudes in summer at latitudes smaller than 60°. This figure represents a typical temperature profile of the layers of the atmosphere. However, the specific profile depends on location, particularly the latitude. There is also a seasonal variation with the tropopause at higher altitudes in summer at latitudes smaller than 60°. The GAP experiment measured the profile over East Central Texas (35° latitude) on May 20, 2008. The GAP experiment measured the profile over East Central Texas (35° latitude) on May 20, 2008.

3. Science Background (continued) The tropopause is characterized by a region several kilometers thick where the temperature is relatively constant. High altitude sounding measurements indicates that temperature over 2 km altitude range varies 3 °C or less. The tropopause is characterized by a region several kilometers thick where the temperature is relatively constant. High altitude sounding measurements indicates that temperature over 2 km altitude range varies 3 °C or less. This figure shows the pressure and density profiles as determined by the NRLMSISE Standard Atmosphere Model. This figure shows the pressure and density profiles as determined by the NRLMSISE Standard Atmosphere Model. The atmosphere may be considered as an ideal gas. The ideal gas law may be used to calculate the density from measurements of pressure and temperature:  = MP/RT. The atmosphere may be considered as an ideal gas. The ideal gas law may be used to calculate the density from measurements of pressure and temperature:  = MP/RT.

4. Science Objectives 1.Identify the zones of the Earth’s lower atmosphere. 2.Determine the altitude of the tropopause. 3.Develop a temperature profile of the atmosphere. 4.Develop a pressure profile of the atmosphere. 5.Develop a density profile of the atmosphere. 6.Compare accepted models of the atmosphere to measurements. 7.Present findings

5. Science Requirements Make measurements every 15 seconds. Make measurements every 15 seconds. Calculate density within 5% uncertainty which includes: Calculate density within 5% uncertainty which includes:  Measure temperature to within 1 °C (0.5% at the tropopause).  Measure pressure to which 1 mbar (5% at the tropopause). Determine the altitude to within 100 meters. Determine the altitude to within 100 meters.

6. Technical Objectives 1.Build and fly a payload and retrieve the data. 2.Measure temperature over the range -80 ˚C ≤ T ≤ 40 ˚C. 3.Measure pressure over the range 5 mbar ≤ P ≤ 1000 mbar. 4.Calculate the atmospheric density using the ideal gas law. 5.Store thermodynamic data in memory contained within the payload control computer. 6. Correlate payload data with mission telemetry data to determine the altitude of each measurement. 7. Compare measurements made by GAP with those made by HATPaC in July 2007.

7. Technical Requirements Payload must remain intact from launch to recovery. Payload must remain intact from launch to recovery. Power system must operate over the temperature range -80 °C ≤ T ≤ 40 °C with the capacity to power the BalloonSat, sensors, and data archive for the duration of the flight. Power system must operate over the temperature range -80 °C ≤ T ≤ 40 °C with the capacity to power the BalloonSat, sensors, and data archive for the duration of the flight. Temperature sensor able to measure over the range -80 °C ≤ T ≤ 40 °C. Temperature sensor able to measure over the range -80 °C ≤ T ≤ 40 °C. Pressure sensor able to measure over the range 5 mbar ≤ P ≤ 1000 mbar. Pressure sensor able to measure over the range 5 mbar ≤ P ≤ 1000 mbar. Record time to 15 second accuracy. Record time to 15 second accuracy. Data archive system with the capacity to store measurements by the sensors and real time clock for the duration of the flight (approximately 750 data records) Data archive system with the capacity to store measurements by the sensors and real time clock for the duration of the flight (approximately 750 data records) Ground system which can download, analyze, and graphically display payload measurements. Ground system which can download, analyze, and graphically display payload measurements.

8. Bad News and Good News

9. Bad News There were some data drop-outs prior to launch There were some data drop-outs prior to launch Capsule landed in a tree Capsule landed in a tree

10. Bad News AD22100 external temperature sensor malfunctioned AD22100 external temperature sensor malfunctioned Diode temperature sensor malfunctioned Diode temperature sensor malfunctioned

11. Good News Payload was recovered Payload was recovered Payload had no visible signs of damage Payload had no visible signs of damage

12. Good News Pressure sensor operated as expected. Pressure sensor operated as expected. Internal temperature sensor appears to have operated as expected. Internal temperature sensor appears to have operated as expected.

13. Results and Conclusions Mechanical and thermal integrity of GAP matched or surpassed that of HATPaC Mechanical and thermal integrity of GAP matched or surpassed that of HATPaC The external temperature sensors malfunctioned The external temperature sensors malfunctioned There may have been significant damage to the instrument suite during touchdown following the ACES-08 flight There may have been significant damage to the instrument suite during touchdown following the ACES-08 flight

14. Acknowledgements PACER PACER LaSPACE, the Louisiana Space Grant Consortium LaSPACE, the Louisiana Space Grant Consortium National Science Foundation National Science Foundation NASA Columbia Scientific Balloon Facility NASA Columbia Scientific Balloon Facility Louisiana State University-Baton Rouge Louisiana State University-Baton Rouge