2013 Fiscal Year Research-status Report
GLONASS-R - A novel method of sensing the environment by means of navigation satellite signals
| Project/Area Number |
25740011
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| Research Category |
Grant-in-Aid for Young Scientists (B)
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| Research Institution | National Institute of Information and Communications Technology |
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Principal Investigator |
ホビガー トーマス 独立行政法人情報通信研究機構, 電磁波計測研究所 時空標準研究室, 主任研究員 (20533798)
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| Project Period (FY) |
2013-04-01 – 2015-03-31
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| Keywords | GLONASS / GNSS-R / sea level / reflectometry |
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| Research Abstract |
The first year of the project was devoted to hard- and software development based on the principles of software-defined radio. This concept enabled me to develop a GLONASS-R prototype system with off-the-shelf components, without the need for dedicated (expensive) hardware. Although all signal processing has been implemented on the software side, real-time operation could be verified already in the first months of the project. After further optimization, bug-fixing and performance tests it was clear that I would be able to test the system earlier than anticipated. After a basic 48h conceptual test at our institute in Tokyo, it was decided to ship the system to the Onsala Space Observatory, Sweden, that has an operational GPS-based GNSS-R system. Over a period of two weeks in October 2013, GPS-based GNSS-R sea-level monitoring and measurements with the newly developed GLONASS-R system were carried out in parallel. In addition, data from co-located tide gauge measurements were available for comparison. With the data taken from the field experiment not only the feasibility of the GLONASS-R concept could be demonstrated, but it could be shown that such an interferometric system can provide sea surface height measurements with an accuracy that is comparable or even better than conventional GNSS-R systems.
For calm sea surface conditions, the GLONASS-R prototype reached an accuracy
of about 1-2 cm, outperforming other GNSS-R systems at that site. A corresponding peer-reviewed paper has been accepted in March 2014 and is currently in print.
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| Current Status of Research Progress |
Current Status of Research Progress
1: Research has progressed more than it was originally planned.
Reason
Soft- and hardware development could be done faster than expected, leading to a working prototype system at the end of the summer. Although field campaigns were planned for the 2nd year of the project, it was decided to carry out a field test already in 2013, since we got the unique chance to do both, test our system for sea-level measurement and validate our concept against tide gauge and conventional GNSS-R systems. The achieved single epoch measurement precision of 1-2 cm for calm sea surface conditions revealed that our system can outperform conventional GNSS-R systems and has the potential to perform even better after small modifications of the signal processing chain.
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| Strategy for Future Research Activity |
With the prototype system ready and tested and promising results from the field campaign in 2013 I am going to carry out further field tests in 2014.
In order to improve the performance when the sea surface gets rough,
a dynamic control of coherent integration length is being planned.
In case of rough swell, longer integration periods could be selected,
leading to a coarser temporal resolution, but significantly improving the accuracy of the system during such periods. This can be implemented straightforward by controlling the integration time in accordance with external measurements, e.g. data from wind speed sensors. The flexibility of a software defined radio allows to adopt the signal processing chain to this new scheme very easily. A similar concept will be used to dynamically adopt the integration period individually for each satellite in dependence of its elevation angle. Satellites at lower elevations can have longer integration times in order to compensate for lower signal strength at those elevation ranges. Field tests in summer 2014 will be conducted again at the Onsala Space Observatory, Sweden where at least three different GNSS-R systems will be validated and compared against each other. Once the system is back in Japan, the prototype system will be used to measure soil moisture changes in an agricultural field. Measurements in winter in northern Japan, enabling the observation of snow heights/depths, will conclude the series of field campaigns and should provide enough data for two new peer-reviewed papers.
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| Expenditure Plans for the Next FY Research Funding |
当初の見積りよりも、経費を削減できたため。
プログラミング用書籍購入予定。
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[Journal Article] Toward a Precise Frequency Comparison with VLBI Technique2013
Author(s)
K. Takefuji, M. Sekido, H. Ujihara, T. Hobiger, M. Tsutsumi, S. Hasegawa, Y. Miyauchi, R. Ichikawa, Y. Koyama, and T. Kondo,
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Journal Title
NICT IVS Technical Development Center News
Volume: N.N.
Pages: 25-28
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[Presentation] First results and next steps of the IAG-ICCT Joint Study Group 0.4 ”Coordinate systems in numerical weather models2013
Author(s)
Hobiger T., Boehm J., Boy J.-P., Desjardins C., Foster J., Gegout P., Haas R. , Ichikawa R., MacMillan D., Ming S.-G., Niell A., Nievinski F., McAdam M., Nordman M., Salstein D., Santos M., Schindelegger M., van Dam T., Vedel H., Wickert J., Zus F.
Organizer
VIII Hotine Marussi Symposium
Place of Presentation
Rome, Italy, Univ. La Sapienza
Year and Date
20130617-20130625
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