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This web site is intended to be useful to all the people involved in the campaign activities carried out in Barrax, La Mancha, Spain, from 12 to 14 of July 2003. Initially, this activities were related with several projects not connected among them, but finally, they have become a joint activity under the umbrella of a formal ESA (European Space Agency) campaign as part of Phase-A Preparations for the SPECTRA mission.
The reason for the selection of the 12-13-14 of July were the coincidence with three consecutive days of CHRIS/PROBA overpasses. Since most of the other planned activities were somehow flexible in dates (more continuous satellite overpasses) the particular orbit of PROBA was the driver in choosing the preferable dates for the campaign.
For those not familiar with PROBA, the satellite was launched in a kind of orbit that has some special features. It makes possible to have coverage over a given site for 2 or 3 consecutive days, and then several days (around 6 at the latitude of Barrax) in between where access to the site is not possible due to the orbital coverage. The situation over Barrax on 12-13-14 July was particularly favourable, because PROBA almost passed over (-4 across-track zenith angle) on 13 July, and then on 12 July (+20 across-track zenith angle) and on 13 July (-27 across-track zenith angle) we had additional multi-angular coverage. Each orbit provides 5 images with different view angles (-55, -36, 0, +36, +55 along-track zenith angles). Then, it seems these were the more optimum dates for the campaign for angular coverage. Overpass times were 11:07, 11:19 and 11:32 for the three days, 12-13-14 July respectively:
Note that 3 multiangular CHRIS/PROBA datasets have been already acquired over Barrax in the previous weeks to the campaign, and the quality of the data is excellent (both geometrically and radiometrically). The plan was to get a multiangular reference dataset with 15 angles (5 angles along each of the 3 different orbits) and 62 spectral channels per angle during this concentrated campaign. This intensive dataset plus the multitemporal series of CHRIS data being collected over Barrax from April to October 2003 will represent the SPECTRA reference dataset for SPECTRA-related studies. Specific atmospheric measurements were planned for each PROBA overpass on each day.
The activities planned over Barrax this summer originated from the combination of a number of initially not connected initiatives coming under different funding:
Moreover, parallel activities related to definition of core sites for satellite validations for CHRIS and ENVISAT data have motivated the interest in getting involved in this activity by other people, with activities also related to AATSR and ASTER thermal data validation. Other team will come from Tunisia to participate in the campaign under the Spain-Tunisia bilateral agreements for cultural/scientific cooperation. The planned tests of the airborne vegetation fluorimeter under construction were not possible during this campaign because the instrument was not yet available, but the technological component of the campaign consisted on the testing of new electro-acoustic detectors for potential use in hyperspectral remote sensing applications (from another EU project). At the end, the activities became relevant enough to go one step forward and try to convert the independent activities into a more coherent program.
For this reason, it was suggested to ESA to convert the different unconnected activities planned in Barrax for this summer into a formal ESA campaign, under the framework of SPECTRA related activities. This idea was accepted, and a formal ESA contract has been established for this campaign.
For MERIS it was only possible to get Full Resolution data for one day during the campaign, 14 July, but at least this image is successfully available:
DLR was in charge of the flights, with aircraft finally available for the 12th of July, one of the days of the CHRIS/PROBA overpasses (and successfully image from the satellite). The sensors used were HYMAP and ROSIS, which are both quite well suited for our activity. The agreement included that DLR will perform the geocoding of all the airborne data (by using PARGE software and all available aircraft navigation/attitude data) while the University of Valencia will perform the atmospheric correction of the data, to make radiometric processing compatible with the procedures applied to CHRIS and MERIS data. Initially, the plan was to acquire one line of HYMAP data (126 spectral channels, app. 5 m resolution) and 4 lines with ROSIS data (115 spectral channels, app. 1 m resolution) simultaneously to the CHRIS overpass by 13 July around 11:20 with flight lines parallel to the principal plane (towards the sun). Finally, it was acquired one more line of HYMAP data (2 in total), and the 4 lines expected with ROSIS, simultaneously to the CHRIS/PROBA overpass but the 12th of July.
Due to the other activities around in the framework of preparations for SPECTRA, and noting that many people involved in the campaign are also involved in parallel SPECTRA studies, it seemed a good idea to put in common such related activities. Most of the activities performed in the campaign are highly relevant for SPECTRA, but in particular the issues related to retrieval of biophysical parameters from CHRIS and MERIS data will be of particular relevance, while scaling issues and complementary between SPECTRA (covering only local sites) and global sensors such as MERIS / SEVIRI are also key elements. Another aspect of the campaign is the use of CHRIS data to test geometric and atmospheric processing procedures to be developed for SPECTRA. CHRIS data also serves for SPECTRA simulation studies, as model-simulated Barrax scenes can be compared with actual data.
With the addition of the airborne component provided by the ESA support, the scaling from ground measurements to the SEVIRI resolution can now be done in with the following progression:
Concerning atmospheric measurements, we launched 2 radiosounding balloons every day of the campaign, one in the early morning (to get stable atmospheric condition) and the other just at the time of satellite/aircraft overpass. The combination of radiosoundings / lidar / sunphotometers / high spectral resolution sky radiance measurements will allow to address a number of issues such as:
Vegetation measurements focused on three main parameters: LAI, fCover, Chlorophyll. These three parameters are the official products being validated in the context of MERIS and SEVIRI activities. Obviously, for validation, it was convenient to measure additional information about canopy architecture: canopy height, leaf size, etc. and other relevant information about phenology of each type of crop. Radiometric measurements at the leaf and canopy levels were performed by using the several available radiometers with different fields of view and different setups. Different methods to measure LAI and chlorophyll were used, as well as for fCover, including regular, hemispheric and stereoscopic digital photos. Some intercomparison of methods was done, as planned, but more will be done.
Maps of the status of vegetation were prepared as part of the background DEMETER activities already on going, and other satellite data (Landsat) were also available as part of the DEMETER project. Since we had already performed two other airborne campaigns this year in Barrax for the TerraSAR program, some aspects of the campaign preparations were well advanced.
| by LEO Group University of Valencia (Spain) || Last Updated: 12 Aug 03 - 19:00h LT |