My (big) mistake wrt LEWIS

Category : Cal/Val, Data, ground measurements

I would like to complement a statement I made on several posts which is inaccurate!

I said on several occasions that LEWIS had been designed by F Lemaitre from ONERA when he actually designed the receiver etc but not the horn which was designed by CNES (M Dejus). I may even add that the design of the horn inspired the design of EMIRAD horn probably and, moreover, was used directly for CAROLS and MARMOTTE2.

This being corrected, I am glad to add hat LEWIS, in the Alps, is still running strong!

SMOS and Lewis to help in SMAP calibration?

Category : Data, ground measurements

Recently (12/2/2015) at 8:43 PST the SMAP radiometer was switched on while viewing deep space and before antenna deployment. The health check was fully satisfactory according to NASA GSFC which is very good news indeed. They are currently busy analysing the results but values look good.

This check can also be used to check the instrument calibration and it was thus decided to do two things on top of what is planned by the SMAP team.

The first one coordinated by François Cabot consisted in doing in a coordinated fashion a SMOS cold sky calibration.

Sky_Feb11track of SMAP when imaging deep sky and point viewed by SMOS during its calibration sequence

The second one was done by Arnaud Mialon with help of François Cabot and François Lemaître and consisted in looking at the same solid angle as SMAP horn with Lewis using SMAP ephemeris. It was done yesterday with apparently success as well.

SMAP_LEWISSMAP ephemeris’s  with those of SMOS and Lewis « box »( F Cabot)

DSCN2153Lewis following SMAP (A. Mialon)

LEWIS on the move: Part 2

Category : Cal/Val, Data, ground measurements

As posted last June our good old faithful LEWIS (Lemaitre et al, 2004) after spending 9 years in SMOSREX near Toulouse underwent maintenance and updating and was moved to Saint Hilaire du Touvet  near Grenoble by François Lemaître and Arnaud Mialon.

The road trip was arduous as LEWIS is not small to say the least while it is « a long and winding road » to the top…

DSCN2069IMG_20140516_081042

DSCN2081

DSCN2087

Once on site (in spite of the snow melt mud) the whole set up with LEWIS and its supporting frame was hoisted and put in place…

And then the connecting testing etc was performed by François while LEWIS was overhanging the valley below….gauging the situation. Enventually Arnaud and François got everything ship shape and the fine tuning started.

The instrument can scan the valley below (Azimuth and elevation and will make continuous measurements on selected spots. Calibration is done as was done during SMOS REX with a few automatic sky measurements performed using a reflective plate (and manual one aiming directly at the sky). In Valley ground measurements are performed on the selected sites and our COSMOS probe will move from Toulouse next spring.

IMG_20140516_120253IMG_0386

We are collaborating with Thierry Pellarin from LTHE Grenoble for this campaign.

First results are encouraging. There are some small RFI but François is devising a scheme to make sure we identify them. The connection between the instruments has also hiccups but here as well Arnaud and François identified the cause and it should be corrected soon.

Our contraption is located close to some para-gliders and we must say they were a bit mystified at the beginning… but the pictures they take from up there are quite nice (this picture was taken by Christian).

Below some first measurements made by LEWIS in St Hilaire du Touvet on the left hand side the temporal plots acquired over a forest and lake mix footprint (some RFI visible). In green the Infra red temperatures and in Red and blue respectively the V and H pol. On the right hand side the view seen by the radiometer when doing these measurements.

lewis_TB_champs_foret_lac_zoom08 nov 14   12h sur Centre2

To finish this story Arnaud made a scan of the whole area and you will see the brightness temperatures (V pol) of the valley as seen from LEWIS  either from above (RHS) or with the perspective (LHS) not the industrial area (coldish due to metallic roofs) the warmish urbanised areas.

lewisTBV_scan_vue3DTBV_scan_vue_dessus

And now the next step is to do some science with this set up… so keep posted!

The funding was partly from SMOS CESBIO but also from CNES TOSCA programme. The Mairie was of very big help and made all what was possible to enable this experiment. The local companies were of great help too and did a mint job … A very big thank to all of them.

Reference

Lemaître, F., J.-C. Poussière, Y. H. Kerr , M. Dejus, R. Durbe, P. de Rosnay and J.-C. Calvet (2004). « Design and test of the ground based l band radiometer for estimating water in soils (lewis). » IEEE Geoscience and Remote Sensing 42(8): 1666-1676.

LEWIS is on the move! Part One

Category : Cal/Val, Data, ground measurements

Back in 2002 we had a high quality ground based radiometer built by ONERA (Jean Claude Poussière and François Lemaître) with CNES funding (TOSCA) (see Lemaitre et al, IEEE). This radiometer was installed in a fallow field south of Toulouse together with classical equipment to monitor the various meteorological and soil variables (see de Rosnay et al, 2006). In 2011 a COSMOS probe was added to the set up  (for more info see here).

LEWIS-Sol

LEWIS during tests before implementation (2002)

From January 2003 to last year the set up worked almost continuously (there was one big maintenance though) providing a wealth of measurements in all possible conditions (wet years, dry years, snow, freezing soils, storms etc….) with L band dual polarised data acquired at angles from 20 to 60° on both bare soil and fallow land.  Moreover, on several occasion we did specific campaigns  for instance to alter roughness over a large range of values etc). This gave way to a number of publications and helped improving LMEB and the L2 retrieval algorithm sub models…

lewis-fauga

Lewis in operation at the SMOS REX site near Toulouse

The data set is available for other research purposes. Just ask if you need part of the data set (yann.kerr@cesbio.cnes.fr). During this whole period, with only one maintenance stop, the instrument worked extremely well with a remarkable stability and accuracy. It even went through a bush fire unscathed!

But after 9 years in operation we decided it might be useful to go to other places and, in collaboration with ONERA (F Lemaître), INRA ISPA (Jean Pierre Wigneron as always since start !) and LTHE (Thierry Pellarin) we looked for, and found, an adequate location close to …

LEWIS_4

The idea was to find a site where we could have more occurrences of snow and cold weather but mainly a set up offering a capacity to have well characterized mixed footprints.

Finally Arnaud and Thierry found a place satisfying all criteria close to Grenoble and we started the move … The first step was to refurbish LEWIS and replace the filters (to reduce RFI risks) this was promptly done in 2012. More complicated was setting up the site as it is located in altitude and we had to have a platform overhanging the valley built, we had to have energy brought to the site and to develop the mechanisms to point the antenna.

radiomètre lewis

Testing the controllers in a warmer (!??) and safer place than on top of the cliff!

This was done during this last winter but we then had to wait for the of the winter and snow melt before we coudl transport and finally implement our equipment on site …

This will be described in part two together with the first plots

download wordpress themes