Introduction

     My name is Brian Ventre, and I am a graduate student at Purdue University, in West Lafayette, IN. Originally from Newark, DE, I completed my Bachelor of Science in Aeronautical and Astronautical Engineering at Purdue in the spring of 2004 and began my Master of Science degree in the same major shortly thereafter.

     My primary area of research is in the use of the Global Positioning System network for remote sensing, particularly during satellite occultations as observed from an aircraft. Professor James Garrison, a faculty member of the School of Aeronautics and Astronautics, is my primary advisor, and we work closely with Professor Jennifer Haase of the Department of Earth and Atmospheric Sciences. Our current project is the development of the GNSS Instrument System for the Multistatic and Occultation Sensing (GISMOS) instrument for UCAR.s High-altitude Instrumented Airborne Platform for Environmental Research (HIAPER) program. GISMOS will record occulting satellite signals and reflected navigation signals from both land and sea to allow for the extraction of water vapor profiles, sea-surface roughness and soil moisture content. By utilizing the illumination of the Earth by GPS and other satellite navigation systems, GISMOS operates passively, without the need for bulky transmitters or heavy equipment. My part in this project is the design and implementation of an open-loop tracking algorithm for the occulting signals to post-process the recorded data and extract bending angle profiles.

     The FORMOSAT-3/COSMIC Science Summer Camp was first brought to my attention by Professor Haase. A student of hers had attended the program in 2004 and gained a great deal from it, which encouraged Professor Haase to recommend that I explore the program. In reviewing the topics to be presented, I realized that this would be a wonderful opportunity to learn more about radio occultation and its use in meteorology. My background is quite different than many of the other students that attended, as I had almost no exposure to meteorology prior to the camp; rather, my background is primarily in engineering and instrumentation, as opposed to numerical weather prediction and use of the data derived from occultation measurements. The summer camp was extremely beneficial in exposing me to the practical implementation of radio occultation data, as well as learning more about the field of meteorology, and will benefit me greatly in my research.

Scientific Experience

     In preparing for attending the FORMOSAT-3/COSMIC Science Summer Camp, I reviewed some of the materials available regarding low-earth orbiting radio occultations, including the predecessor missions to FORMOSAT-3/COSMIC, such as GPS/MET and CHAMP. Through these, I gained some familiarity with the methodology of radio occultation; however, this knowledge was greatly enhanced and expanded over the course of the week-long camp.

     The process of radio occultation is in concept relatively simple, but becomes quite complicated in practice. As a broadcasting source.a GPS satellite, in most current cases.begins to rise or set relative to a receiver.either another satellite or an aircraft.the radio signal will begin to pass through more of the atmosphere. While the speed of electromagnetic waves in a vacuum is a well-known constant, the atmosphere will appear to change that speed, introducing excess phase shift at the receiver. Also, the radio wave will not travel in a straight line; instead, it will .bend. due to prismatic effects of water vapor. This bending appears in the phase shift as well, and it is this shift that forms the basis for radio occultation measurements. The excess phase shift is mathematically related to the bending profile and from there to a water vapor profile of the atmosphere. This profile is of great benefit to forecasting and research as it can be assimilated into numerical weather prediction models to determine validity and improve results.

     In reality, signal multipath, super-refraction, and atmospheric variability make this a difficult problem to solve. A number of the lectures during the camp discussed these issues, and I learned a great deal about the practical implementation of radio occultation measurements. The use of radio-holographic methods to reduce multipath, quality control of results, problems introduced by the different paths taken by L1 and L2 signals, and error estimation were all quite useful topics and well explained.

     One of the most interesting experiences for me was to visit Taiwan.s National SPace Program Office and see the FORMOSAT-3/COSMIC satellites undergoing preparations for launch. As an engineer.and an aerospace engineer at that.the opportunity to observe flight hardware was quite exhilarating. The ingenious packing method, which will allow 6 of the platter-shaped satellites to be launched with a single rocket yet end up in unique orbits, was also of great interest to me. Having had exposure during my schooling to orbital mechanics and gravity effects, I was nonetheless surprised at the complex but simple method of orbital separation that has been chosen for COSMIC. It is always exciting to me to be able to observe real-world applications of scientific principles, and I believe that this experience in particular combines so many of the subjects I have worked in as to be a very unique experience which I am glad I had the good fortune to participate in.

     As I noted above, I had very little exposure to meteorology prior to the Science Summer Camp, especially in the areas of numerical weather prediction and data assimilation. In addition to the engineering and measurement lectures that I discussed previously, a number were also given on the incorporation of the data products from FORMOSAT-3/COSMIC. This was my first introduction to the workings of numerical weather models, and I found it very interesting how measurements are integrated into the predictions they provide. I had always assumed that measurements were incorporated into the model as starting parameters, and then compared at the end to check for discrepancies in the model. However, the discussions of data assimilation, where measurements are used merely to apply corrections to the model, were an interesting discovery for me. Another fascinating point was the lecture on what level of data to use, and how to avoid including too many assumptions by processing the model towards the measurements, as opposed to making the measurements into a data type the model had already produced.

     On Tuesday afternoon, all of the US students were given the opportunity to present their research and discuss their posters to any interested parties. I found this experience to be very rewarding, as it allowed a great deal of interaction between the speakers and students, as well as encouraged both the US and Taiwanese students to learn about each others. work. In observing the posters and talking with the students who had produced them, I was impressed by the breadth and depth of their knowledge. I also enjoyed being able to discuss my own research with a number of the speakers and students, particularly as my research area is more instrument and engineering focused than others were. In addition, many of the speakers were able to offer useful insights into possible difficulties in investigating the topics presented, and their experience was greatly appreciated. Overall, I believe that the opportunity for the students to present their work was beneficial from both a scientific and personal level.

     Perhaps one of the largest scientific benefits I gained from the Science Summer Camp was a better understanding of my own research. Prior to attending the camp, I must admit that while I understood how radio occultation measurements were made, I was not fully aware of how these measurements would be used, beyond merely providing certain numerical products. As such, I had no clear understanding of what data researchers who relied on these measurements require. Given that my research is to actually make radio occultation measurements and not to employ them in a meteorological sense, it would be unfortunate if these measurements were of no use to a meteorologist. After being exposed to the methods of data assimilation, uses of numerical weather models, and the goals of meteorologists, I believe that I have a much better grasp on the requirements and needs of the user. It is one thing to merely produce data, but another to produce useful results that will benefit others. Through my formal and informal interactions with the Taiwanese and US students, as well as the speakers, I believe that my research will benefit greatly by producing results in a useful form and with an understanding of their goal.

     The Science Summer Camp experience was very valuable to me, and I gained much by attending. The science applications of radio occultation, in particular, are much clearer, and I better understand the goals of both the FORMOSAT-3/COSMIC program and my own research. The scientific opportunities afforded to me by this trip were immense, and ones of which I am most grateful.

Cultural Experience

     Before the Science Summer Camp, I had never had the opportunity to travel to Asia. My previous international travel was limited to Western Europe, which, while different from the United States, is generally considered culturally more similar to the US than are Asian countries. Exposure to the Taiwanese culture and people was a very interesting experience and one that I value.

     During the course of the week that we were in Taiwan, we were fortunate to have the voluntary assistance of a number of local university students. Their help in guiding us through the subway systems, navigating markets, negotiating with vendors, and suggesting good restaurants was invaluable, and also an interesting experience in and of itself. All were very friendly, and we had the excellent opportunity to form friendships and talk about both scientific and personal topics. These were particularly evident during our excursions to the Taipei weekend flower and jade market and our trip to the Hua-Lien weather station. The Taipei weekend flower and jade market is held below one of the overhead freeways and is a huge collection of greenery and jewelry, all available for sale and negotiation. It was all a sight to behold, and our guides were very helpful in explaining many of the cultural reasons behind the items we saw. Vincent, one of the Taiwanese students who traveled with us for the week, explained that because of the extremely high population density of Taiwan.s western coast, public green space was at a premium. As a response to this, many Taiwanese would shop at the flower market to purchase plants for their apartment homes, providing a sense of space and comfort. I had the opportunity to speak with him at length again during our trip to the Hua-Lien weather station, which we traveled to via train. The three-hour trip was a wonderful time for all of us to talk with the other students and explore the similarities and differences in our cultures. We spoke about government, politics, climate, businesses, inter-personal relationships, holidays, and a number of other topics that really gave each of us insight into the other.s country . and even our own, as explaining often lead to interesting questions and lines of thought.

     Another benefit from our trip to the Hua-Lien weather station was the opportunity to see more of the country of Taiwan than just Taipei. The capital city of Taiwan, Taipei is home to nearly 3 million people and is a closely packed urban landscape. Although it is home to the world.s tallest building at 508 meters, Taipei 101, many of the surrounding buildings were no taller than 10 stories, and the city seemed to lack the core of towering skyscrapers that characterize New York City and Chicago. It was a very different city than either of those, extremely clean, with almost no litter or public trash receptacles. Snarled with traffic.particularly motorcycles.it was a modern city that moved very quickly. Hua-Lien, located on the east coast of Taiwan, is much smaller and nestled in the verdant and mountainous terrain that characterizes the island.s Pacific coast. Life was much calmer on the coast, and Taiwan.s location as a sub-tropical island was much in evidence in the abundance of trees and plants. The contrast between the two was incredible, and quite illuminating. It really allowed me to expand my view of the country and understand the various cultural forces at work.

     Another cultural experience that we had was the Shihlin night market. It is one of the largest in Taipei; filled with people, food, shops, and entertainment, it is a uniquely Asian experience, as our hosts explained. I had the opportunity to visit twice in the company of our Taiwanese hosts. They were excited to show us their culture, and I, for one, was excited to take part in it. Games, unique foods, and the people all made for an experience that is almost impossible to replicate in the United States. We tried Taiwanese sausage, chicken steaks, spicy cold noodles, stinky tofu, shaved ices, Chinese pancakes, various fruit drinks, and other foods that I can.t even describe. Many were dishes unique to Chinese and Taiwanese culture, and while I must admit that I won.t be trying stinky tofu again, they were all an experience in and of themselves.

     The trip to Taiwan was an incredible experience, and exposure to its culture was invaluable in broadening my understanding of the world. From friendships with the Taiwanese students to experiences in culture, I think that the entire journey was one that I will treasure for a long time to come.

Concluding Remarks

     What I.ve written above can only contain so much of my overall experience. There is much more that I gained, and only so much of it can fit on so many pages. The entire trip was eye-opening in both scientific and cultural ways, and I cannot express enough my thanks to the NSF, UCAR, NCAR, and NSPO for their support, as well as the dedicated staff of the COSMIC office for planning and accompanying us.

     As is probably obvious by now, I think that the FORMOSAT-3/COSMIC Science Summer Camp was a wonderful opportunity, and one that I am profoundly grateful for being invited to attend. From interactions with both the Taiwanese and US students to meeting and talking with many of the experts in the field of radio occultation, this program has had a positive influence on me. I fervently hope that future travelers will also be able to benefit, and look forward to seeing their own stories unfold in the years ahead.