Cal/Val Portal

Site measurements – Day nine 25/08/10

2013-08-20T14:37:07Z

Day nine, our last day, finally arrived. A busy morning had been planned as in addition to the usual site characterisation measurements the participants were also going to measure the so-called “Thome” strip. This comparison was the brainchild of Kurt Thome. The idea was to get the participants to measure the reflectance of a short strip of the lake quickly, one after the other and in as short as time as possible.


Preparing to measure the "Thome" strip	Measuring the "Thome" strip

A section of the lake along the edge of site M5 was chosen. Those participants that used a continuous sampling method went first, followed by the teams that measured at discrete points. The continuous samplers then measured the site again. Before each measurement the participants measured their white reference panel before measuring the site. The comparison was successfully completed in under 20 minutes.

After the “Thome” strip measurements the participants measured a number of the sites with the overpasses of satellites SPOT 5, Deimons 1 and THEOS of interest to a number of the teams.

During the past 9 days the nine individual sites were measured a total of 65 times and there were at least 40 satellite overpasses. That’s a lot of data!

Our participants!

A big thank you to all the participants who took part in the site measurements over the past nine days. They are, in no particular order;
NPL (UK): - Andrew Deadman, Shuang Li
CMA (China): - Yuan Li
CSIR (South Africa): - Derek Griffith
GISTDA (Thailand): - Morakot Kaewmanee, Amornchai Prakobya, Chaichat Musana
INPE (Brazil): - Flávio Ponzoni
KARI (Korea): - Yun-Gon Lee
ONERA (France): - Yannick Boucher, Françoise Viallefont, Philippe Rolland
SDSU (USA): - Dennis Helder, Larry Leigh
Tubitak (Turkey): - Hilal Özen, Vedat Gün, Ramazan Küpçü, Soner Büyükatalay + many more!
VITO (Belgium): - Sindy Sterckx, Els Knaeps

Also thank you our two drivers, Yousef and Lutfu who drove us to from Aksaray to Tuz Golu and back every day.

Site Measurements - Day Eight 24/08/10

2013-09-19T08:10:57Z

Day eight arrived with beautiful clear skies and no hint of clouds. The day turned out to be as good as if not better than yesterday. After we arrived on site we caught up with Derek and Shuang who had stayed the night in the camp.


GRASS at sunset	GRASS at night

It turned out they'd had quite an eventful afternoon/evening. During the afternoon they experienced the shock wave from an explosion that they had heard. We're still not sure what the cause was. Shuang made quite a few measurements during the night on GRASS, the last at 0230! We should have some interesting data. It was quite a cold night too by all accounts.


ONERA adjusting their radiometer	The team from Tubitak measuring the NPL panel

The site measurements continued as they have done for the previous seven days. The overpass of satellite SPOT 4 at 0824 was of interest to quite a few of the teams and they planned their measurements accordingly. The radiometer comparison of yesterday was repeated today as we took advantage of the favourable conditions. Hopefully the data will also be favourable. Tomorrow is the last day of site measurements but is still going to be a busy day as there are at least six satellite overpasses of interest to the teams.

Site Measurements - Day Seven 23/08/10

2013-09-19T08:12:58Z

Day seven dawned with a new member to add of this intrepid bunch of scientists. Kurt Thome, from NASA, joined us last night. He has a strip of the salt lake named after him. This is quite an acheivement for someone who hasn't even visited the lake before! Kurt brought the good weather with him as today was certainly the best day we've had so far and the others haven't been bad either. The prospect of a good day meant that this was an ideal day to perform another site-based comparison


South Dakota's Larry Leigh setting up his radiometer	A GISTDA scientist measures the NPL panel

This time we would be comparing the radiometers. NPL's large reflectance panel was to be viewed by all the participant's radiometers, one after the other. This comparison relies on the conditions being stable and today was as good a day as any. The measurements each team peformed were the same as those done in the laboratory on 15th August. It went well, all the measurements were completed within 50 minutes. The participants seem keen to repeat this exercise so, conditions permitting, we will do it tomorrow.


Who called the Ghostbusters?	The radiometer head from INPE, Brazil

Shuang Li and Derek Griffith are staying at the camp tonight. Shuang is going to make some measurements of the BRDF of the lake at night using a light source provided by ONERA, France. We hope it isn't too windy or cold, or that they don't have to make too many trips to the toilet!

When you got to go, you've got to go!

Site Measurements - Day Six 22/08/10

2013-09-19T08:15:45Z

Day six dawned with high hopes. The skies were very clear and the team from GISTDA, Thailand finally had their equipment, it being delivered the evening before. The conditions were the same when we arrived at Tuz Golu. Those at the camp however had endured a windy night. So much so that when we arrived at the camp after our morning strole across the lake (!) the Turkish hosts were busy repairing the tarpaulins that mark out the site as they had been blown about during the night.

More clouds!

The clear conditions didn't last though as clouds started to appear. There were probably more clouds than on the previous day. Nevertheless the conditions appeared to be relatively stable so the site characterisation continued. The team from China were calibrating the 1 km x 1 km site again as they had another satellite overpass today. Around noon we repeated the reference panel calibration from yesterday. Analysis of the previous day's data had revealed some anomolies.


Derek Griffith with his reference panel	GRASS in its new location

In order to sample another part of the site, GRASS was moved from its first location to another about 200 meters to the north-west. This was accomplished with the help of Dennis Helder and Larry Leigh from South Dakota State University and two of our Turkish friends. It was a relatively easy task, we simply disconnected the optical fibres and other connectors, lifted the base ring and walked to the new location. Measurements at the new site were also made today.

Everyone is keeping well, and no one has been sunburnt. Everyone does have rather brown hands though!

Site Measurements - Day Five 21/08/10

2013-11-15T13:43:09Z

The concept of the weekend didn't occur to the participants who, as far as they were concerned, today was day five not Saturday! Although the Yuan Li from the Chinese team did have the day off today. Breakfast was a sombre affair as we awoke to some clouds and it didn't look much better in the direction of Tuz Golu.


Cloudy skies	The ONERA bicycle-powered radiometer

When we arrived we were pleasantly surprised as there were relatively few clouds, however it didn't last as they did begin to bubble up throughout the morning. Even so the planned in-situ reference panel comparison went ahead, just after noon local time, and was repeated as the first measurement was done without the panel from ONERA as they were still measuring the 1 km x 1 km site, on bicycles!


Andrew Deadman measuring the CSIR panel	Flavio Ponzoni from INPE, Brazil, positioning his panel

The format of the panel comparison was that one radiometer, the one from NPL/ONERA was set up to view the NPL panel at nadir (normal to the surface). The participants panels were then measured in turn, with the NPL panel measured again after each of the participants panel. A similar process to the laboratory measurements. In order to minimise the effects of the changing sun zenith angle, the measurements were done close to local noon (where the changes are smallest) and quickly; the whole process took 15 minutes. In a further attempt to account for any irradiance changes Derek Griffith from CSIR South Africa, offered to measure the irradiance using a cosine receptor he has for his ASD instrument. The irradiance was monitored throughout both the comparison measurement runs and encouragingly the initial results show that the irradiance varied by within ±1 % for most of the measurements.

Site Measurements - Day Four 20/08/10

2013-09-19T08:25:27Z

Day four and still the slightly hazy conditions at the measurement site were there to greet us. Once again we had the 3.5 km walk from the drop-off point to the measurement site, although our bags were taken ahead of us by the quad-bike and trailor combination.

Arriving on site

Some teams were continuing with the site characterisation part of the comparison while others were concentrating on satellite calibrations. Some were attempting to do both. There were eight different groups characterising the site today, measuring seven of the nine individual measurement sites.


Measuring downwelling radiance	Automated sunphotometer

Further measurements were made with the GRASS instrument and an analysis made of the downwelling radiance measured. This is a new capability and is due to a new radiometer that had recently be used with GRASS. It was developed by the University of Edinburgh and enables GRASS to make upwelling radiance measurements from the ground almost simultaneously with the downwelling radiance measurements from the sky. This is important as site characterisation measurements should really be made under stable conditions. Early results show that the conditions, particularly close to local noon are quite stable. If the conditions at near noon tomorrow are similar then the first of the on-site cross-comparison measurements will be made. This is where we will replicate the laboratory comparison measurements but in the field.

The sunphotometer on site is part of the Aeronet network and among others things helps determine atmospheric optical depth. This is an important parameter in satellite calibration.

The team from VITO (Sindy Sterckx and Els Knaeps), are leaving tomorrow, this was their last day on site. A photograph of the current particpants is shown above. Also Françoise Viallefont from ONERA has joined the campaign. She is replacing Yannick Boucher who is leaving early on Sunday morning.

Site Measurements - Day Three 19/08/10

2013-09-19T08:26:34Z

Day three arrived all too soon and before we knew it we were on the road again back to Tuz Golu. The participants are staying in a very nice hotel in Aksaray. Trouble is it is about 90 km from the site and the journey takes about 90 minutes. As a result the minibuses leave the hotel at 0700 sharp. However we were one bus down today as the driver was taken sick. We wish him a speedy recovery.

If they say there's a salt shortage, don't believe them!

The conditions on the lake were better than previous days; a little clearer (and hotter!). But there was still a general haziness around. Of interest to a number of teams today was the overpass of satellites Landsat 7 at 08:11 UTC, SPOT 4 at 08:20 UTC and THEOS at 08:36 UTC among others. As a consequence two teams were characterising the 1 km x 1 km site.


Measurements, South Dakota style	The Turkish team prepare for "battle"

After dinner in the hotel, the participants discussed the day's measurements and also agreed on the plan for tomorrow. It was a fairly successful day, once one of the teams measuring the 1 km x 1 km site were shown which direction it was in! All agreed it was the hottest day so far!

Site Measurements - Day Two 18/08/10

2013-09-19T08:27:10Z

Day two arrived with the participants knowing which of the sites they were going to measure as this had been decided the night before in the hotel. Slightly cloudy conditions greeted the teams when they arrived at the salt lake with lots of high cirrus clouds. This can make the downwelling radiance vary quite a lot. Ideally these measurements should be made in stable conditions.


South African and Brazilian scientists measuring the site	The French team from ONERA

Seven sites were measured today with the overpass of satellite Landsat 5 at 08:17:15 UTC of particular interest to a number of the teams.

GRASS measuring reflectance panel

The GRASS instrument was finally up an running after a number of minor problems. It is now able to provide data on the BRDF (Bi-directional Reflectance Distribution Function) of the salt lake. This data is very useful for scientists involved in satellite calibration.

The feedback from the teams was that today was more successful in terms of data collection, although some did complain about the heat! Unfortunately there isn't much we can do about that.

Site Measurements - Day one 17/08/10

2013-09-19T08:27:50Z

So the first day of measurements has arrived. Again the participants had the long walk to the measurement site to contend with first before doing any measurements. A brief meeting was held to decide which team was measuring which site.


Participants at briefing

The site has been marked using marker flags into nine seperate measurement areas. There are eight areas that are 300 m x 100 m and one area that is 1 km x 1 km. The entire measurement site itself is marked by two black tarpaulins that are 120 m from the edge of the smaller measurement areas. This is so the measurement site can be identified by orbiting satellites. A plan of the measurement site is show below.


Measurement site	Marker flags

Seven of the teams present measured six of the measurement sites. The 1 km square site is large enough to be measured by more than one team. The participants were on the lake from approximately 0930 local time to 1230 local time. A few teams had some problems communicating with their equipment and as a result didn't manage to make as many measurements as they would have liked. However there are still a further 8 days of measurements to come in which to gain more data.


Weather station on site	VITO (Belgium) measurements in progress

Some satellite images of Tuz Golu that were taken on day one have already been received. The tarpaulin markers can clearly be seen in both images. These images can be seen in the multimedia gallery calvalportal.ceos.org/web/guest/multimedia-gallery

Travel to Tuz Golu and set up of equipment

2013-09-19T08:30:04Z

On 16th August the participants gathered at Tubitak Uzay to supervise the loading of their equipment for the trip to Tuz Golu. At approximately 1000 the participants left Tubitak Uzay for Tuz Golu.


The participants outside Tubitak Uzay	The participants board the minibus

Then it was the 2 hour drive to Tuz Golu. The journey was incident free, unlike the comparison last year when the minibus got a punture shortly after leaving Ankara. The minibus arrived at the salt lake at approximately 1200. Lunch was provided by and eaten at the salt works.


Tuz Golu	Harvesting the salt

Then it was off to the measurement site. This site is 3.5 km from the salt works. Transport was provided for the equipment but the participants had to walk. Except Andrew Deadman from NPL who was lucky enough to hitch a ride whilst accompanying NPL's equipment to the measurement site.


Equipment transport vehicle	On the way to the site

Upon arrival at the site it was time to set up the various equipment. NPL were providing a BRDF measurement system know as GRASS (Gonio RAdiometric Spectrometer System), South Dakota State University a shadow band radiometer and Tubitak Uzay a Sunphotometer and weather station.


The "base" camp at the measurement site	Setting up the shadowband radiometer

The GRASS instrument takes quite a lot of time to set up and with help from Shuang Li and Selime Gurol the task was completed in a couple of hours. Problems with the electrical generator meant that it was not possible to test if GRASS was working. That's the first task for tomorrow.


GRASS before...	...after

Radiometer Calibrations

2013-09-19T08:30:45Z

The second day of the laboratory measurements involved the calibration of all the participants radiometers. These are the actual instruments that make the measurements in the field. It is therefore important to know if there are any discrepancies in the calibration of these instruments. This was done via a calibrated radiance source. The source, a Transfer Standard Absolute Radiance Source or TSARS for short, was provided by NPL for this purpose. It is calibrated directly against national standards.

Transfer Standard Absolute Radiance Source (TSARS)

The participants were briefed by Andrew Deadman from the pilot lab, NPL, before the measurements began. The fibre optic input from each participants radiometer was set up in the pre-aligned "pistol grip" in front of TSARS. The "pistol grip" was used in order minimise any effects due to mis-alignment. The measurements from each radiometer were repeated a number of times.


Andrew Deadman briefs the participants	Larry Leigh, SDSU, careful inserts the fibre optic into the "pistol grip"

More pictures from the radiometer calibrations can be seen in the Multimedia Gallery at calvalportal.ceos.org/web/guest/multimedia-gallery .

There were two groups who were not able to measure TSARS. The group from Thailand whose equipment had still not arrived, we are hoping it will arrive tomorrow, and the group from Brazil who have an instrument without a fibre optic input. This instrument will however be set up to measure TSARS when these measurements are repeated after the field measurements on 26 August.

Tomorrow, 16th August, all the participants together with the hosts from Turkey, will travel the 150 km or so to Tuz Golu, the literal translation of which is salt lake. Here the participants will brave soaring temperatures while they set-up their equipment in readiness for the 9 days of measurements on the lake that will follow.

Reflectance panel calibrations

2013-09-19T08:31:28Z

Today was the first day of laboratory measurements. The aim here is to get a handle on any differences in the calibrations of the instrumentation and reflectance panels that are routinely used during measurements in the field. This is done by comparison to transfer standards provided by NPL that are directly traceable to primary standards. The standards used are a Transfer Standard Absolute Radiance Source (TSARS) and a calibrated reflectance panel.

Things didn't start too well as the computer that controls TSARS failed. This meant a change to the program on the first day! The reflectance panal calibration was brought forward a day to allow time for a solution to the TSARS problem to be found.

Reflectance panel comparison

All the participants panels were compared to the NPL reflectance panel using a 45°/0° source/detector geometry. The source was an NPL 1kW FEL tunsten halogen lamp and the detector was an ASD spectroradiometer that ONERA in France have kindly loaned to NPL for the duration of this campaign. The panels were measured over the full range of the spectroradiometer, 350 nm to 2500 nm.


Lamp/panel geometry	Detector/panel geometry	Andrew Deadman aligning one of the reflectance panels

I am pleased to report that the TSARS problem has been solved. Thanks must go to John Mountford at NPL who sent all the required files along with detailed installation instructions, that not even Andrew could get wrong(!), that enabled Andrew to install the required software on another computer. When tested TSARS was working well, phew!

Welcome and Kick-off meeting

2013-09-19T08:31:58Z

All the participants arrived safely in Turkey and gathered for the kick off meeting at the campaign hosts Tubitak Uzay. Dr. U?ur Murat Lelo?lu from Tubitak Uzay welcomed the participants to Turkey and gave a brief introduction to Tubitak Uzay


Dr. U?ur Murat Lelo?lu welcomes the participants to Turkey	The participants at the kick-off meeting

Then Andrew Deadman from the campaign pilot laboratory, NPL (UK) briefed the participants on the rationale for the campaign and also briefly described the measurements that would be made over the next two weeks. After Andrew, Hilal Özen from Tubitak, described the logisitcal arrangements and how they are going to get all the scientists and their equipment from Ankara to the middle of Tuz Golu, over 150 km away. She also presented the latest satellite overpass information.


Andrew Deadman briefs the participants	Hilal Özen tells the participants about Tuz Golu

The participants were then able to inspect their equipment, to see if it had arrived safely. No damage to report, thankfully!

The participants and hosts then enjoyed a very nice dinner at a nearby restaurant which had stunning views over Ankara.