Abstracts from the 2016 AHAC conference

This is a listing of Abstracts from AHAC 201

Applying Newton’s Law of Cooling When The Target Keeps Changing Temperature, Such As In Stratospheric Ballooning Missions

Newton’s Law of Cooling describes how a “small” system, such as a thermometer, comes to thermal equilibrium with a “large” system, such as its environment, as a function of time. It is typically applied when the environment is in thermal equilibrium and the conditions are such that the thermal decay time for the thermometer is a constant. Neither of these conditions are met when measuring environmental (i.e. atmospheric) temperature using a thermometer mounted in a payload lofted into the stratosphere under weather balloons. In this situation the thermometer is in motion so it encounters layer after layer of atmosphere which differ in temperature, and the changing environmental conditions can influence the thermal decay time “constant” for the thermometer as well. We have used Newton’s Law of Cooling in spreadsheet-based computer simulations to explore how thermometer readings react under these conditions, to better-understand how logged temperature records from stratospheric balloon flights during both ascent (relatively slow) and descent (much faster, especially at altitude) are related to actual environmental temperatures at various altitudes

Data Analysis and Curve Fitting to Determine the Regener-Pfotzer Maximum

Various data analysis methods were explored to more accurately and consistently determine the Regener-Pfotzer (RP) maxima for high altitude cosmic radiation. The radiation has been measured during 15 balloon flights using Geiger counters with five second accumulation times. Of the 15 flights, 10 of them included omni-directional counts data, and 8 of them included vertical coincidence counts data. Count data from altitudes greater than 10 km were analyzed to determine the maxima. The data analysis methods used were moving average filtering and summation of Geiger counts into one minute intervals. Moving average filtering did not give reliable results, so the summation method was chosen. Once the data were summed, several different curves were fit to determine where the RP maximum occurred. The curves tested include second and third order polynomials as well as cubic spline interpolation of the data averaged over 1 km intervals. Second order polynomial fitting did not fit the data well. Third order polynomials and cubic splines gave better results. Third order polynomial fitting was chosen due to its ease of use and the similarity of the results given by the cubic spline interpolation (within 1%). The omni-directional RP maxima occurred at an average altitude of 21.8 km ± 1.7 km, while the vertical coincidence RP maxima occurred at an average altitude of 18.5 km ± 1.1 km. In addition, the vertical coincidence RP maximum occurred at 65 hPa ± 9 hPa, while the omni-directional coincidence RP maximum occurred at 38 hPa ± 13 hPa

The Regener-Pfotzer Maxima during a Total Solar Eclipse

The Regener-Pfotzer (RP) maximum is the altitude at which cosmic radiation intensity is the greatest. A reduction of the altitude of the interaction layer, assumed to be measured by the RP maximum, has been suggested to account for a reduction in the secondary cosmic ray flux measured at the surface of the Earth during a total solar eclipse. To investigate this suggestion, high altitude cosmic radiation was measured using Geiger Mueller (GM) counters carried beneath weather balloons both before and during the total solar eclipse on August 21st, 2017. The pre-eclipse omnidirectional RP maxima occurred at an average altitude of 20.2 km and 20.4 km during the eclipse. The vertical coincidence pre-eclipse RP maxima occurred at an average altitude of 18.3 km and 18.0 km during the eclipse. Our results do not show any reduction in the altitude of neither the omnidirectional nor the vertical coincidence RP maxima outside the range of our observations before the eclipse

Using Thermocouple, Thermistor, and Digital Sensors to Characterize the Thermal Wake Below Ascending Weather Balloons

In this paper we present additional results from our on-going research effort to characterize the thermal wake that trails below ascending latex weather balloons on flights into the stratosphere; a wake which interferes with the ability of temperature sensors in payload boxes hanging from the balloon (and hence enveloped by the wake) to correctly measure the ambient temperature of the atmosphere through which the balloon is ascending. A “wake boom” is used to measure temperature variations up to 1.5 m horizontally from varying distances directly below the neck of the balloon. Results to date agree with the literature that especially above the tropopause the thermal wake is warmer than the ambient air during daytime ascents, due to solar radiation warming the balloon skin, but colder than ambient air during night-time ascents, due to adiabatic cooling of the gas inside the balloon (which also occurs in the daytime, but is smaller than the daytime warming effect). In particular we report on thermal wake characterization using (Neulog) thermocouple sensors, as compared to (HOBO) thermistors and (Arduino-logged) DS18B20 digital temperature sensors. We also present additional results from X-shaped 2-dimensional wake booms or “X-Booms” which allow us to compare wake temperatures on the sun side versus the shade side of the balloon, looking for asymmetries in the horizontal temperature profile

Thermal wake studies during the August 21st 2017 total solar eclipse

A thermal wake occurs when a high altitude balloon (HAB) influences and changes the surrounding ambient atmospheric temperature of the air through which it passes. This effect warms the air below the balloon to greater than ambient temperatures during daytime flights, and cooler than ambient temperatures during nighttime flights. The total solar eclipse of August 21st 2017, provided us with an opportunity to study these balloon induced temperature transitions from daytime, to eclipsed induced night conditions over the time scale of a single flight. To measure these transitions, St. Catherine University and the University of Minnesota, Morris, flew over 40 temperature sensors suspended beneath weather balloons ascending within the path of totality. Stratospheric temperature data collected during the eclipse show evidence of both daytime and nighttime wake temperature profiles

Minnesota Space Grant Consortium

The National Aeronautics and Space Administration (NASA) Office of Education solicits proposals for the NASA National Space Grant College and Fellowship Program. Each funded proposal is expected to increase the understanding, assessment, development, and utilization of space and aeronautics resources. The program promotes partnerships and cooperation among universities, federal, state, and local governments, and aerospace industries to encourage and facilitate the application of university resources to aerospace and related fields

Stratospheric Studies Using High Altitude Ballooning

Erick Agrimson, Associate Professor of Math & Physics, received a $3,244 Faculty Research & Scholarly Activities Grant to support a project to investigate the stratospheric wake effect with at least six high altitude balloon flights

MN Space Grant 2018-2019

In support of the MNSGC, St. Catherine University (St. Kate’s) will focus on curriculum and delivery in introductory physics courses and courses outside of the physics program to increase NASA related content and skills in areas of interest to NASA. We will also continue to build our high altitude ballooning research program with projects related to thermal and radiation measurements in near space, programming, equipment building and troubleshooting as well as teamwork and communication skills. These areas serve NASA’s strategic goals of hands-on space (in our case, near space) research as well as outreach and professional development with female students