Partner Organizations: Centre National d'Etudes Spatiales: In-kind Support; Collaborative Research
Engineers and technicians under the guidance of Philippe Cocquerez from the Centre National d'Etudes Spatiales (CNES) in France are involved as partners in this project. CNES is the lead platform development organization for the project called Concordiasi which will operate out of McMurdo Station, Antarctica. CNES's super-pressure balloons will be used to launch our instruments which will circulate in the Antarctic stratospheric vortex for periods up to 20 days. CNES is responsible for all data telecommunications between the ground station and the balloon payload, as well as base payload design, payload temperature control, and payload battery and power design and consumption.
Other collaborators:
Concordiasi is a joint French-US initiative consisting of 16 long duration balloon flights from McMurdo Station in 2009. Investigators involved with the instruments to be deployed include scientists from Météo-France, Centre National de la Recherche Scientifique, Laboratoire de Météorologie Dynamique (LMD), National Center for Atmospheric Research (NCAR), Purdue University, University of Colorado, and UCLA. We have had some contact with scientists from LMD and engineers from NCAR for planning and instrument development purposes.
Activities and findings:
Research and Education Activities: The major research activity in 2008 has focused on testing and troubleshooting of various instrument components in cold temperature and low atmospheric pressure environments over an extended period of time. Because of the duration of these balloon flight missions, and the limited power available to operate the instruments, power will be cycled on and off at both regular and user-defined intervals. Thus the instruments will cold soak for long periods between relatively short operational periods. Our aerosol instrument consists of three main components: 1) an optical particle counter (OPC) to generate laser illumination of the scattering chamber and to measure the intensity of scattered light in 8 size channels for particles passing through the chamber, 2) a data acquisition and instrument control system, and 3) a pump to bring air into the scattering chamber. The OPC is built by Particle Metrics Inc, with specific modifications in the detection thresholds to achieve a proper size range for atmospheric aerosol. We then are responsible for final calibration of the size channels and for preparing the OPC for high altitude (low pressure) operation. The data acquisition and control system has been developed from a commercial microprocessor and components by Stan Smith at Wyoming. The pump is the same pump used in our mid latitude OPCs. These three components were tested for environmental limitations (pressure and temperature) and for lifetime. Optical particle counter (OPC): Pressure Testing:: Concordiasi experimental conditions require that instruments be powered on and off at altitude. This means, because of the cold temperatures, that the voltage needed to start the laser is much greater (13,000 volts instead of 6,000 volts) than a laser started on the ground. The higher voltage can cause arcing. To eliminate this possibility, high voltage components within the instrument were potted After potting each instrument was tested in a pressure chamber at 13 hPa to check for arcing and for laser operation. Following this test each laser was checked for subsequent leaks of the He-Ne laser. Temperature testing: There are two main concerns here. First to determine the temperature threshold at which OPC components may fail. Second, colder operating temperatures may introduce a bias into the size of the particles sampled. Instruments have been tested between temperatures of -10 to -40ºC. Data acquisition and control system (DACS): The DACS's main purpose is to query the OPC for data, buffer the data, then format and forward the data, using the data protocol supplied by CNES, to CNES's telemetry system. Due to power constraints the DACS also controls the power sequencing for bringing the OPC and pump into operation. The DACS also monitors voltages and temperatures to insure proper operation, and uses signals from the CNES system to synchronize an internal clock to time stamp our data. To accomplish this required a DACS controller with the following properties: RS232 port to interface to the OPC, internal memory large enough to buffer the data, RS485 port to interface to the CNES system, analog to digital input to monitor the pump temperature, inlet temperature, laser voltage, and main input voltage, digital outputs to control the power switching. an internal clock, and low power consumption. The best fit for the requirements is a Rabbit Flex 3810. An additional interface board was added to buffer the analog signals and temperatures, and for power switching relays. This DACS system was tested for operation with the OPC at cold temperatures and found to operate satisfactorily. Pumps and motor: The pumps have been tested for long term wear and low temperature effects. Various seals (fiberglass, thick Teflon, thin Teflon, and none) were tested in the pumps to optimize cold temperature performance. The pumps were then life tested at -10ºC. Mechanical design and integration with the larger CNES balloon gondola: Using 3-D drawings of the gondola and instrument, scientists and engineers from Wyoming and CNES have been working remotely to determine, within the gondola: instrument configuration, component connections, electromagnetic shielding, weights, power consumption, duty cycles, and communication between the gondola and the operator on the ground. Final agreements, designs, and technical documents are nearing completion.
Findings: OPC: Pressure testing: All lasers passed the tests at low pressures. All lasers operated, no arcing was observed, and no subsequent leaks of the He Ne gas were found.. Temperature testing: The lasers operate normally at -10ºC. The one test in which the instrument was cold soaked at -55ºC and then warmed to -40ºC for testing resulted in a failure. The laser operated and the instrument was sensitive to particles; however, the thermal gradients at such cold temperatures caused a leak in the laser tube and the helium leaked out over the next several days. Further tests are required to more clearly define the temperature threshold for successful operation between -10 and -40ºC. It is anticipated that the gondola temperatures will be maintained at approximately -20ºC. Limited particle testing of the units at such temperatures to check for size shifting are inconclusive at this time. Laboratory experiments to more carefully address this possibility are planned. DACS: This board operated normally at temperatures as cold as -40ºC and there are no pressure restrictions. Pump Testing: Low temperature tests: The pumps begin to draw extra current when temperatures drop below -40ºC, thus the operating temperature range (~ -20ºC) should have little effect on the power requirements for the pumps. The thin Teflon seals gave the longest lifetime and all pumps were rebuilt with these seals. The pumps were found to have a life span of about 20 hours with a 30 liter per minute (lpm) flow and > 40 hours with a 10 lpm flow. As a result, two instruments will be flown with 10 lpm pumps and two with 30 lpm pumps. Also, the DACS has been designed to allow pumps to be turned on only when the OPC has been sufficiently warmed up, which should extend pump life. Interface/Mechanical design and integration: University of Wyoming personnel are planning to travel to CNES's laboratories in February 2009 to physically integrate the Wyoming OPC with CNES's gondola system and to complete environmental tests of the complete gondola.
Training and Development: Stephanie Luberda, an M.S. student, has gained experience in collecting and analyzing laboratory data to evaluate aerosol pump life spans and cold temperature tests. Stan Smith has gained experience in developing a data acquisition and control system, and in designing environmental chamber tests. Lou King has gained technical experience in performing those tests. Yong Cai has gained technical experience in completing laboratory calibrations of OPCs.
Outreach Activities: Plans for Concordiasi were summarized in the following scientific seminar presented in 2008: Earth Sci. Dept. Seminar, U. of N. Colorado, 'Antarctica's Ozone Hole: Is It Really Shrinking?', January 2008, presented by Jennifer Mercer Plans for Concordiasi were summarized in the following lay lectures presented in 2008: Science Lecture at McMurdo Station, Antarctica 'Antarctica's Ozone Hole, Is It Improving?', September 2008, presented by Jennifer Mercer University of Wyoming Summer Engineering Program Lecture, U. of Wyo., 'Antarctica and the Ozone Hole', June 2008, presented by Jennifer Mercer
Journal Publications:
Other Specific Products:
http://www-das.uwyo.edu/~deshler/
The link to the research projects provides a brief description of the research planned by the University of Wyoming within the Concordiasi project. The link to publications provides access to work published.
Contributions to Education and Human Resources:
Staff scientists, engineers and technicians have gained experience working as a team at their home base and remotely with teams of scientists and engineers at the CNES laboratory in France. The distance, and language barrier, have proven to be challenging, but the two teams have worked together to facilitate communication and to make progress. One graduate student has gained experience in evaluating laboratory data.
Special Requirements for Annual Project Report: