Exchange Report by Tobias Stangier

Project affiliation: Infrared Heterodyne & Planet Science
Supervisors: Prof. Dr. Lucas Labadie, Dr. Manuela Sornig, I.Physikalisches Institut, University of Cologne
Hosting institution: NASA Goddard Space Flight Center, Planetary Science Division, Greenbelt, MD, USA,
Dr. Theodor Kostiuk, Dr. Tilak Hewagama
Duration of stay abroad: 22.10.2012 – 25.11.2012
 

Introduction

At the beginning of my career as a doctoral candidate was the question, whether it is possible to retrieve valuable information on the atmospheric properties of our neighbor planet Venus and Mars by analyzing CO2 absorption features.

A manifold of physical parameters are hidden in the line shape, such as abundance of the molecule, pressure and temperature of the gas and dynamics in the atmosphere. The profile of single ro-vibrational transitions is difficult to observe. An ultra high resolution spectrometer is needed to resolve the narrow frequency rage in which the transition is located. The Tuneable Heterodyne Infrared Spectrometer (THIS) of the I.Physics Institute is able to achieve the necessary resolving power of ν/∆ν > 107 in the mid-infrared wavelength regime around 10μm. The instrument is successfully applied since many years for observation and investigation of planetary atmospheres.

However, the investigation of the CO2 absorption lines in the Venusian atmosphere has never been target of interest in the past. To this point, only the sunlit side of the planet has been investigated, giving emphasis on the dynamics in high altitudes. The intention was to change that!

At an early stage, it got clear, that the retrieval of dynamical properties from the absorption lines is almost impossible, since an incredibly high signal to noise ratio would be needed. Hence, the focus now was on the retrieval of vertical temperature profiles.

The idea was to implement an inverse retrieval method to deduce the thermal properties from the lines. Our group has a model at hand which was especially designed and written for heterodyne observations of planetary atmospheres in the mid-infrared. The model is called CODAT and models the beam-integrated radiative transfer through the targets atmosphere. CODAT was developed by a group at the NASA Goddard Space Flight Center in Maryland, USA. Head of the group since the mid-80s is Dr. Kostiuk, who is in charge of the other, currently operating infrared heterodyne instrument in the world, HIPWAC (Heterodyne Instrument for Planetary Winds and Composition). The radiative transfer code was written by Dr. Hewagama in the early 2000s. It was initially intended to model the absorption lines on the basis of a known temperature-profile. Thus, the code had to be modified in order to extract the temperature-profile from the data.

A close collaboration between the two groups in Germany and the US has been established in the past decade and thanks to the SFB 956 student exchange support, I had the great opportunity to travel to Goddards and work together with our colleagues. The journey was just at the right time in the course of my PhD and I spent 5 intense weeks during which a milestone for the success and the outcome of my research way laid.

Experiences

The work abroad was basically performed by Dr. Hewagama and me. We worked together to achieve the goal to implement a routine the for temperature retrieval. In the first days we discussed the feasibility of the mission and how the goal could be achieved within the short time frame of 5 weeks. We agreed, that an inversion routine has to be created. Dr. Hewagama did most of the programming, since he was the expert on the model.

My job was to test the program and find errors and instabilities which made it crash. For that purpose, I needed a computer and network access. That is not as easy as it sounds in an US governmental facility as NASA. It took more than one week until I had the permission to use the NASA network and I lost a lot of valuable time.

However, first test runs were very promissing and we iterated the program through 4 versions, until we finally found a mode were the program seemed to run stable and we retrieved reasonable output. For sure, without the good team work, this could not have been performed as quick and as succesfully. From than on, all further work had to be done back in Germany, but the whenever questions arise, Dr. Hewagama is willing and able to help and support in any possible way.

Conclusions

The experiences during my stay abroad where nomerous. The chance to work at NASA was a great opportunity, which I hoped to get since a long time. The administrative restraints are much higher than in a German university and it was interesting to see how a non-educating facility handles science and research. Thus, the close collaboration between the colleagues from NASA and me tought me a lot on the everyday life of a scientist outside of Germany. Also, the importance of international, professional relationships got a lot clearer to me. I am very greateful for this unique opportunity.

Besides the work that was done, it was also an adventure to manage the small things as lodging and food with a limited budget. In the spare time, there was the chance to travel around and discover many interesting places and locations in the vicinity of the US capital. At the weekends, when the center was closed, I could visit i.e. Washington D.C., Baltimore, Philadelphia or the Blue Ridge Mountains. I would recommend every PhD candidate to take advantage of this chance. It will certainly contribute to your professional and private development by a great deal. And for me, it was absolutely necessary to achieve the goals in my thesis and, in retrospective I need to confess, it probably would have taken much longer for me to finish.

Current position

Since 2014 Tobias works as the Product Assurance Manager for Space Applications for Radiometer Physics GmbH. For that he needs to coordinate the quality management of the company in the frame of the MetOp-SG Satellit Mission and the Jupiter Icy Moons Explorer (JUICE).