REPORT ON OVERSEAS VISIT - I BARTON -
NOVEMBER-DECEMBER 1996

ITINERARY
22 November Hobart - London
25-29 November Rutherford Appleton Laboratory
1 December London-Munich
2-3 December CEOS WGCV IVOS Sub-group meeting at DLR
4-6 December CEOS WGCV Meeting
6-8 December Munich - Hobart


RUTHERFORD APPLETON LABORATORY (RAL)

Meetings with scientists

A series of meetings was held during the week to discuss joint scientific programs based on the analysis and applications of ATSR data. More details on these meetings are available on request.

Albin Zavody - Discussed the new SST and cloud-clearing algorithms for the re-analysis of ATSR data. A paper was under preparation detailing the new cloud-clearing scheme. Differences between ATSR and ATSR-2 data products were discussed and methods for investigating these differences evolved. New data files were obtained to extend the RAL atmospheric transmission model to wider spectral bands in the near and thermal infrared.

Chris Mutlow - Discussed future validation plans including the possible use of Australian waters for international campaigns. The collaboration with Iwate University at Mutsu Bay in North Japan had suffered from persistent cloud cover and some logistic problems. Chris was also taking over from I Barton as the Chairman of the CEOS IVOS sub-group (see below) and details of the hand-over were arranged.

Phil Watts - Phil is planning to spend some time at DAR in the near future and possible research programs were investigated. These must fit in with his responsibilities and research activities at RAL as well as with the programs at DAR. Fred Prata is the point of contact at DAR.

Myles Allen - Discussions on the applications of altimeter data in oceanography including techniques for combining ATSR and ALT data. We also talked about future techniques for the best analysis of ATSR data. It was agreed that the best techniques were probably those detailed in my recent paper just submitted to JGR. Copies of this paper were left at RAL.

Ryuzo Yokoyama - While I was at RAL Professor Yokoyama was also visiting so we talked about the Mutsu Bay campaigns as well as the possibility of Yokoyama attending the series of meetings being set up for Townsville in April 1997. If he attended these meeting he would try and bring a high resolution infrared camera to obtain some coincident measurements with the AIMS radiometer installed on the wave-piercing ferry.

Tim Nightingale - Tim has built a new infrared radiometer for SST validation and had used it at Mutsu Bay. The new radiometer was inspected and provided some possible modifications to the CSIRO models.

Data requests

ATSR-2 data were requested for Fred Prata to cover two volcanic eruptions as well as the data for the DC-8 campaign over the Hay and Amburla test sites.

A request was lodged for full mission Australian continental coverage for ATSR-1 data. This request would be forwarded to NERC and we are waiting for a response. It is likely that this request will be filled when ESA and RAL start their full ATSR reprocessing program.

RAL also agreed to forward some ABT files as soon as they were available. These files are required to enable continuation of the ATSR water vapour derivation studies.

Other contacts

David Llewellyn-Jones (Leicester Uni) - Phone discussions regarding plans for AATSR meetings in Townsville during April 1997. A draft notice was formulated and has been circulated to likely attendees. The notice is included as Attachment 1.

Cathy Johnson (UK DoE) - Cathy is replacing Peter Mallaburn as the DoE person in charge of the AATSR program. A courtesy phone call was made to introduce myself and to discuss the status of the AATSR Science Agreement between CSIRO and DoE. Changes are required to the document since the demise of the ASO and these would be finalised at the Townsville meeting in April.

CEOS MEETINGS - DLR, OBERPFAFFENHOFEN, GERMANY

NOTE:

CEOS = International Committee on Earth Observation Satellites

WGCV = Working Group on Calibration and Validation

IVOS = Infrared and Visible Optical Sensors Sub-group

CEOS WGCV IVOS meeting

The two day meeting was chaired by Ian Barton. The minutes of this meeting are included as attachment 2. Twelfth CEOS WGCV meeting

This meeting was attended as the Australian representative on this Working Group. The minutes of this meeting will be available in due course.

Significant Items

Two significant actions were discussed at the CEOS meetings involving the intercomparison of data from different satellite instruments using a particular ground test site. These activities could extend to other test sites in the future.

The Libyan Desert was selected as the land-based test site and Chris Mutlow at RAL was to coordinate the collection of data over this site for a selected time period. The results of this activity would be discussed at the next IVOS meeting.

Ian Barton suggested the Townsville wave-piercing ferry transect as an ocean based test site. This has now (Jan. 1997) been agreed with William Skirving at AIMS and Chris Mutlow at RAL. A fixed time period would be selected to collect data over this site - probably in mid-1997 to provide cloud-free conditions and time to ensure that the collection of good ground-truth data was possible.

ATTACHMENT 1

DRAFT PLAN FOR TOWNSVILLE MEETINGS - APRIL 1997

Dear All

Herewith is a draft plan for meetings in Townsville next April. Can you please let me know if you can make these meetings and whether there are others who should be invited (David, Should you pass this on to all the AATSR SAG, - especially the ESA members?). William Skirving has agreed to look after some of the local arrangements and we will advise of hotels and meeting places when we have an idea of the number of participants.

I hope you can all make it! Regards, Ian.

Draft Plan for AATSR-Related Meetings in Townsville - April 1997

Below is a list of possible attendees at a series of meetings to be held in Townsville during the week of 7 - 11 April 1997. Any comments on the proposed meetings, the list of attendees and the times allowed will be most welcome.

The meeting schedule will allow for travel to Townsville on Monday afternoon to give a full day for meetings on the first 2 days. The best ATSR-2 pass is on Thursday 10 April (Sunday 13 is better - but too late) so we will all participate in a validation exercise on that day. Please let me know if you will be able to bring a radiometer on the Field Excursion to the Barrier Reef.

Please let me know if you are likely to attend these meetings and whether there are others in your institute that may attend.

Activities:
  1. AATSR Mini-SAG meeting.
Half-day Day 1.
  1. Visit to AIMS
Half-day Day 1
  1. AATSR Science Agreement DIST/CSIRO/DoE/VEGA 2 hours
Evening Day 1.
  1. Australian AATSR Science Team Meeting
Half-day Day 2.
  1. Future Global SST and LST Validation Plans for AATSR
Half-day Day 2.
  1. Visit to Barrier Reef validation site*
Full day Day 3


* The outward trip to the Barrier Reef validation site will coincide with an ATSR-2 overpass. Collection of ground truth data by small portable infrared radiometers will be possible. AIMS and CSIRO will explore the possibility of deploying larger radiometers during the trip to the Barrier Reef. Also, the return trip will coincide with an AVHRR overpass - so let's hope for clear skies!

Possible Participants:
Australia CSIRO B Embleton

J Huntington

D Jupp

A.Prata

I Grant

A Pearce

I Barton
AIMS W. Skirving
BoM J LeMarshall
ANTCRC N Young

K Michael
DIST ????
UK RAL C Mutlow (and/or ??)
Leics Uni D Llewellyn-Jones
Notts Uni M Steven
NERC S Briggs
DoE C Johnson
VEGA H Kelliher

H Tait
Japan Iwate Uni R Yokoyama


ATTACHMENT 2

Seventh CEOS WGCV IVOS Meeting
Minutes
DLR, Oberpfaffenhofen, Germany
December 2-3, 1996

Agenda
Monday 2 December
1000 Welcome, introductions and logistics of meetings
1010 Meeting Objectives, Review of Agenda
1020 Minutes of Last Meeting and Discussion. Review of Action Items
1100 Report from CEOS Plenary
1115 Agency/country reports - Coffee
1245 Lunch
1400 Status of Calibration Test Sites Dossier. Interaction with NASA Group
1430 Status of On-board Calibration Techniques & Facilities Dossiers
1500 Discussion on status of Strategic Plan. Review of IVOS activities.
1530 New initiatives, Establishment of an IVOS data set. Suggestions for future special sessions.
1600 Presentation from P. Teillet on a new paradigm for cal/val
1700 Recommendations to WGCV
1715 Discussion on Tuesday's agenda
1725 Next meeting

Tuesday 3 December
0900 Presentations by Drs David Robinson and Nigel Fox
1000 Discussion on standards and traceability
1030 Coffee
1050 Special session on future validation plans. Introduction, aims, outputs.
1100 Presentations to special session
1245 Lunch
1400 Presentations continue
1530 Discussion on special session activities
1630 Formulation of special recommendations to CEOS Working Group on Cal/Val (WGCV).
1715 Final comments, future meetings
1730 Close


Welcome

On behalf of DLR and DARA Wolfgang Noack welcomed the participants in the IVOS meeting and explained the logistics of the meeting and associated activities.

Introductions went round the room and the Chairman passed on regrets and apologies from Karl Staenz, Allan Hollinger, Wayne Boncyk (who was represented by Dennis Helder), Masanobu Shimada and Zhimin Zhang.

The Chairman noted that it was unfortunate that no one from NASA was attending as the dossier is a key component in IVOS plans and activities.

Objectives/Agenda

The Chairman outlined the agenda items and suggested that an important component of the day's activities was to ensure that the Dossier compilation and maintenance was progressing well. The second day's sessions would include presentations from the National Physics Lab. in the UK and a special session on the validation of future satellite instruments.

The agenda was accepted without modification.

The Chairman informed the meeting that he was standing down as Chair and that Chris Mutlow had accepted the offer to become the new Chair. The Chairman thanked all the IVOS participants for their contributions over the past five years and seven meetings and wished Chris all the best in his new role.

Review of Minutes from Previous Meeting

The Chairman reviewed the minutes of the previous meeting. He noted that the two recommendations presented to the plenary were accepted with modification and some discussion. The recommendation that ``satellite operators provide reliable on-board calibration'' was discussed and Plenary asked for the recommendation to be more specific with a definition of on-board calibration. For test sites the action is on WGCV members to go back to their agencies and propose international test sites and to foster the use of the proposed test sites.

Much discussion about this topic centred on the fact that CEOS doesn't provide any funds for activities and thus, what kind of recommendations WGCV can make? Alan Belward noted that if IVOS developed recommendations with greater specificity then the plenary and sponsoring agencies may be more likely to accept and support the recommendations. Kumar asked what the criteria for a CEOS-endorsed test site is? Garth Morgan suggested that the sites listed in the dossier should be considered CEOS- endorsed, although funding to maintain the sites (e.g. collection and archiving of ground data, etc) will have to come from each agency. Mike Rast suggested that the dossier is compiled for information purposes and that some effort needs to go into selecting test sites and developing cross-calibration plans, etc.

Review of Action Items

IVOS-3-1. Still open - but will be replaced by ACTION IVOS-7-1 with a reminder that all IVOS members should notify the WGCV Secretariat with information on new campaigns and instruments. Alan Belward says that when the information is available it should be emailed and hosted on or linked to the CEOS-WGCV web page.

IVOS-4-6. Outstanding. Will be replaced by ACTION IVOS-7-6.

IVOS-6-1. Closed. The Chairman commented that he welcomed the attendance of Guiseppe Zibordi and other Ocean Colour folks as this will help with the co-ordination of their activities. He also suggested that it was unrealistic for agencies to send more than one or two representatives to IVOS meetings and it was thus the responsibility of those attending to represent their agencies interests in a wider range of cal/val activities than their own special areas of interest.

IVOS-6-2. Outstanding. Will be replaced by ACTION IVOS-7-2. At present there is a limited number of test sites on the Dossier and a special effort would be made to ensure that this component of the Dossier was expanded.

IVOS-6-3. Outstanding. Replaced by ACTION IVOS-7-2.

IVOS-6-4. Closed.

IVOS-6-5. Closed.

IVOS-6-6. Closed.

Report from Plenary

The new Chairman of WGCV (Alan Belward) briefly reviewed the results of the plenary meeting. A key item is that the affiliates now have a mandate for greater participation in CEOS working groups. The plenary wants to know what the consequences of the recommendations will be on the working groups. WGCV is encouraged to address cal/val recommendations emanating from the Sept 96 In-situ Observations for Global Observing Systems, Geneva. These recommendations were directed towards the end user and geophysical (derived) data sets, and contained fundamental cal/val issues. Rao stated that we should stay away from algorithm specifications and focus more on basic sensor calibration and radiance. Phil Teillet however noted that the funding reality is that the focus needs to be on end-user product validation. Rao argued that only operational algorithms should be considered for validation - experimental algorithms being too unbounded.

Agency/Country Reports

Chris Mutlow - RAL, UK. ATSR-2 has been resurrected and has been operational for some time. ATSR-2 calibration has been confirmed and validated using several methods including:

on-board calibration

vicarious calibration - desert sites

vicarious calibration - deep convective clouds

GOME comparisons

sunglint

All methods confirmed ATSR-2 pre-flight calibration except 1.6 micron channel which was off by a factor of 1.4 An error was discovered in the pre-flight calibration calculations and the following correction results were very good. Chris discussed the ATSR-2 instrument characterisation. They use an on-board visible calibration which views the sun each orbit for calibration. Using both White Sands and the Libyan desert sites has resulted in consistent results and they have also done some cross-calibration with AVHRR measurements over the Libyan desert sites with good results. In addition, comparisons with aircraft underflights have been very good in the IR and good in the vis/near IR.

Rao - NOAA, USA. The new AVHRR/3 instrument will have a new channel 3a (1.58-1.64 micron) for aerosol products. This will change the basic data formats which will impact operational processing and calibration. AVHRR/3 will also have a sun shield to limit stray light contamination. Rao reviewed the AVHRR Libyan desert calibration noting that the values are tied to U2 aircraft underflights which minimise atmospheric contamination. All of this information is available and kept current on the NOAA web site. Rao is also looking at test sites in Nevada USA and the Gobi desert. Ross Mitchell from CSIRO will be looking at desert sites in Australia.

In ensuing discussion it was noted that spatial homogeneity, temporal and seasonal consistency, consistent elevation, access to the site for ground-based collaborative measurements and no BRDF contamination are important for any vicarious calibration test site.

Phil Teillet - CCRS and IGBP. The Canadian report had been submitted in hardcopy. Phil did discuss one urgent topical issue. He noted that some BOREAS sites may be maintained for 3 years and will be available to cal/val activities, however others are being closed. A final decision will be made in December and IVOS members should immediately notify Phil of any interest in these sites.

Guiseppe Zibordi - EU. Guiseppe discussed the CoASTS project - Coastal Atmosphere and Sea Time Series project. This involved the collection of measurements over the north Adriatic Sea to support SeaWiFS and OCTS. This has also involved evaluating bio-fouling of underwater radiometers as well as intercomparison of atmospheric and marine radiometers.

Oaku - NASDA, Japan. ADEOS cal/val briefing. Much work is being done on detector normalisation and characterisation. For OCTS, the on-board calibration is being used for trend analysis only at this time; users will need to use pre-launch information until vicarious and buoy data are available.

Mike Rast - ESA. ERS; GOME cal/val is nominally complete though more work is being done now that algorithms are changing. ENVISAT; MERIS calibration work ongoing; they have had two additional diffuser plates developed and will be shipped to GSFC for comparison. MERIS is also looking into options for vicarious calibration test sites. Mike noted that a recent issue of Remote Sensing of the Environment includes a paper of desert test sites for optical satellites and Mike circulated a good reference book (by Kramer). Ian noted that these should be added to the proposed CEOS WGCV bibliography.

Action: Mike to circulate the study on cal/val strategies to the IVOS group pending review of the study.

Lasse Pettersson - Norway. Lasse described ALOMAR; a lidar facility at 69N which collects year round ground-based atmospheric parameters to study the arctic atmosphere including thermal and chemical parameters for trend measurements. ALOMAR is collecting a long-term baseline data set as well as campaign-specific measurements. An ALOMAR and GOME calibration exercise is underway. They would like to use OCTS data in this work since SEAWIFS will not be available for some time.

Dennis Helder - SDSU / EROS Data Center. EROS are characterising TM through the internal calibrator. They are looking within an orbit, in a 30 day outgassing cycle, and through the instrument life. They have also looked at several night scenes to identify and correct the ``memory effect'' of the calibration pulse (memory effect being up to 2 DN). EROS is also looking at pulse decay effects. Lifetime degradation of the calibration lamps is being investigated. Landsat 5 has lost forward scan calibration pulses. LSAT 7 is similar to LSAT 4-5 and is scheduled for May 98 launch. The Enhanced (?) Thematic Mapper (ETM) has a 5 % absolute radiometric accuracy which should be double earlier TM sensors. ETM will collect sun view data once per day and will have a full solar calibration once a month. LSAT7 processing will correct for affects identified in the earlier satellites. A Landsat TM Radiometry page has been prototyped at

http://iplab2out.sdstate.edu/tmcal

Stephen Tjemkes - Eumetsat Operational calibration of Meteosat: Currently here is no onboard calibration performed for Meteosat. Since the blackbody cannot be used. In future (Meteosat 7) the onboard blackbody calibration can be utilised, however it is inserted into the optical path with a mirror such that not the whole optical path can be calibrated. For the calibration of the VIS channel aircraft observations and model calculations are used. Since the spectral response function of the VIS channel is rather wide, the calibration is scene dependent. Therefore, clouds, sea, vegetation and desert (Tunisia) targets are used for the vicarious calibration. The estimated error in the aircraft observations are 5 %. The independent calculations by the Matrix Operator Method also shows 5 % uncertainty.

Analysis of the calibration coefficient of the two infrared channels depicts minor problems with the current adopted cloud detection method. The calibration of the IR window channel relates digital counts over clear ocean areas to radiances calculated using a radiative transfer model with SST analysis, and ECMWF forecast data. The uncertainty in the calibration coefficient is estimated to be 1% with a possible 1K bias in the radiance. The WV channel calibration relates the clear sky area digital counts to radiances calculated using a radiative transfer model adopting collocated radiosondes. Therefore in addition to the problems with the cloud detection method, the vicarious calibration of this channel is also dependent on the quality of the radiosonde observations. The precision of the current calibration coefficient is about 3% with a possible 5% bias.

Eumetsat is planning satellite intercalibration for all three channels. For the VIS channel this involves the Meteosat 5, Meteosat 6 and where possible the AVHRR. For the two infrared channels this involves the HIRS instrument and AVHRR.

Calibration Test Sites and Dossier Status

Several members noted that information that had been supplied for inclusion on the WWW was not there. Alan Belward thus suggested that we make a specific recommendation that specific information which we have submitted be made available on the web. Ian suggested that 10 or so sites could be identified for immediate inclusion on the web. These should be vicarious calibration sites. Validation sites such as Hapex, Sahel and Boreas will be addressed later. Phil Slater suggested that vicarious calibration sites such as these be considered level 1 sites, and product validation sites be considered level 2.

The following sites were identified along with those persons to be responsible for supplying the test site information to the NASA representative who maintains the WWW site.
LAND SITES
White Sands US (Slater, Biggar)
Lunar Lake US (Slater, Biggar)
Railroad Playa US (Slater, Biggar)
Lake Tahoe US (Slater, Biggar)
Ivanpah Playa US (Slater, Biggar)
Dun Huang China (Z. Zhang]
Qing Hai Lake China (Z. Zhang)
Hay Amburla Australia (Prata, Mitchell, Barton)
Strezlecki Australia (Prata, Mitchell, Barton)
La Crau France [Adragna)
Spanish Sites? Spain (Adragna)
Libyan Desert Egypt (N. Rao)

OCEAN COLOUR
MOBY Hawaii (Dennis Clark)
Venice Tower Italy (Zibordi)
PlyMBODy UK (Zibordi)
Japan Sea Japan (Oaku)
IR/TEMP SITES Mutsu Bay Japan (Mutlow)
Ocean Sites Australia (Barton)
Sudofex UK (Mutlow)


Action: For these sites, the identified folks will get a copy of the form off the web, send to J Butler, with a copy to Alan Belward and the WGCV Secretariat by 1 March. These will be updated on CEOS web site (by 1 July) and the progress of the dossier site will be monitored. Phil Slater noted that it's important to advertise campaigns to better utilise resources. There was some discussion about the applicability of some of the ocean sites.

Discussion on Future Special Sessions and Activities

An IVOS Data Set

The Chairman proposed that IVOS could select 2 sites and a time period and collect all the data available from all sensors.

Kumar noted that if CEOS takes it up, all data should be provided free.

The Chairman suggested that we could start collecting data now and India investigate the possibility of doing the work as part of taking the secretariat in a year's time. There was then some discussion about data availability. Alan suggests that we should identify the level of effort it would take for compiling and analysing the data. All agreed that this should be undertaken.

Specialist Sessions

Rao suggested a special session on on-board calibration systems for the next meeting. The Airborne RS conference in Copenhagen in July 97 has a special session/short course on imaging spectrometer calibration and correction. Phil Teillet suggested that hyperspectral calibration in general should be considered for a future session.

Phil Teillet's New Paradigm in Cal/Val

Phil started his presentation by stating that users will only use data products if the calibration was transparent to their application. He then discussed the spectral and spatial resolution of various instruments. For instrument calibration there are only a few operational cases. Generally atmospheric correction is non-operational, but requires well calibrated data and timely, ready access to atmospheric parameters. In the past little attention has been paid to spectral characterisation but this is required to generate geophysical parameters from different instruments. Phil also discussed geometric effects, viewing directions, topography, scan angle, resampling, etc. These all have a big effect on information content.

Users: Special users do their own preprocessing and require high accuracy. Operational users need good cal/val for further work, but don't want to know abut cal/val. The majority of users need stability and quality but don't really know about cal/val. Existing algorithms do not meet the needs of operational users. To get to the majority of users it is necessary to be clear about what is being offered. For Remote Sensing, one needs reliability of supply, plug and play, and data quality (consistency, quantitative and comparable).

A future strategy should take account of research, reference sites, demonstration, QA focus, standardisation, accreditation and communication. Phil also suggested that we think laterally; e.g., recommend that all future instruments include specific common channels. Ground truth areas of 10KM x 10KM area are needed to compensate for current problems in calibration. Data should be hyperspectral, measured from a low altitude aircraft. Phil also introduced the Quantitative Stability Reference (QUASAR) Concept in which hyperspectral data ($10-$15K per flight) are collected. This would be followed by radiometric, spectral and geometric processing of the data. Phil hopes to begin some flights in 97 and expand his activities in 98. He would then generate products (surface reflectance and at-sensor radiance, and NDVI and biophysical) and distribute site statistics on a CCRS web site one week post-flight. The results would also be available as wall-to-wall data sets on CD-ROM one month post-flight.

For this activity the site considerations are; uniformity, flatness, and size (10x10km). Primary sites would be in prairie grasslands in Canada and Nevada.

With this New Paradigm the immediate action should be on the communication aspects. In particular web sites and the dossier should be improved and kept current.

Important questions to be considered are: error budget, site selection, spatial resolution, imaging calibration, etc. Infrastructure questions are: availability of instrument, turn-around time, who participates. Phil then showed several images to illustrate potential sites and highlighted subtle differences in and among sites.

Discussion: Phil Slater endorsed this new idea as he believes the funding for on-board calibration will soon be drying up.

Chris Mutlow noted that many instrument characteristics will not be identifiable without on-board calibration. Specifically, build up of condensation during outgassing cycles can't be observed by campaigns.

Phil Slater then asked about a joint field campaign in Nevada and several expressed interest in participating including UK/RAL, CCRS, NASDA, and possibly NOAA. A meeting to discuss this would be held in February next.

3rd December 1996

Country/Agency Reports (contd

China. The Chairman read the highlights of the China country report which was submitted by Zhimin Zhang who was unable to attend due to problems with getting a Visa. The full report would be placed on the WGCV site on the WWW.

Presentations by NPL, UK

David Robinson and Nigel Fox - UK National Standards Laboratory.

David Robinson gave an introduction to NPL - it is the UK's NMI (National Measurement Institute - any country's official measurements institute). NPL has about 600 scientists, more than 95 years in operation and maintains all 7 SI units (Kg Mt Sec K Amp Candela Mole). NMIs establish international equivalence of standards as well as R &D contracting and technology transfer.

Scope of NPL's space measurement activities:

Optical thermal instruments,

RF/microwave/millimetre wave,

time and frequency,

problem solving and other measurement services.

Importance of space standards; continuity, traceability, and terrestrial equivalence.


Nigel Fox started his presentation by discussing Accuracy vs Precision; accuracy is how well a measurement is known compared to an internationally agreed standard or scale while precision is how well a measurement can be repeated. Accuracy is less than precision but accuracy enables different instrument measurements to be compared, allows long term validity of data sets, and enables compatibility with other terrestrial data (e.g. ground- based radiometers equivalent to space-based, and finally reduces room for argument. E.g. fibre optic power showing that calibration efforts have resulted in much higher accuracy. Nigel explained the standards verification and traceability process and how the measurements are filtered out to the user community.

Limitations to accuracy are that the NSL does not understand user-specific requirements,, and space scientist don't understand options available from NSL and of course time and budgets are always limited. The various assumptions made in the interpretation of optical measurements from space using pre-flight and in-flight calibration (TIR black body, VIS/NIR Lamp & Diffuser) were listed. Solar calibration and vicarious methods were then discussed. Steps to obtaining a calibration baseline from a National Standards Lab and the sources of error in this calibration information from irradiance scales, BRDF, etc were then described. NPL have developed a new technique to reduce errors and improve dissemination of calibration to the community. This involved reducing uncertainty using a new radiance standard (using a new cryogenic radiometer) and reducing the length of the calibration chain. Nigel provided details on current calibration methods in use.

Direct radiance measurements using filter radiometers for both VIS/NIR and TIR have been shown to reduce measurement errors. These transfer radiometers are portable, robust, vacuum compatible, quick and cheap, and highly accurate. One drawback is that the number of channels available can be limited. This was followed by a discussion of accuracy of field calibration and options for field calibration.

Discussion: Availability; the portable calibration standard for visible is available now, depending on the specific channels requested. NRL can also calibrate participant's own radiometers as needed.

Action: Nigel and David to forward a list of relevant references and the Chairman encouraged them to publish details of their new technique in a scientific journal.

Phil Slater(EOS Calibration Scientist) is also planning to form an EOS Calibration Panel sub-group to co-ordinate and oversee all EOS-related vicarious calibration activities.

The Chairman thanked both David and Nigel for their presentations and was sure that the new technique would soon be adopted by those using transfer standards to assess the performance of space instruments.

Special Session on Future Validation Plans

Phil Slater - MODIS calibration

Phil gave details of the plans in place for EOS instrument cal/val. In particular he discussed the calibration of the short-wave channels of the MODIS instrument. Two techniques will be used - reflectance-based calibration and radiance-based calibration. He described the errors involved in the calibration procedures and detailed the traceability of the measurements using transfer standards. A list of proposed intensive field campaigns was given along with plans for pre-launch cal/val activities using ground-based test sites in the western US. Hard copies of the presentation "Validation of MODIS-derived top-of-atmosphere spectral radiances by means of vicarious calibration" were made available at the meeting.

Mike Rast - MERIS Cal/Val Activities

Mike reviewed the 15-band MERIS instrument characteristics, the System Performance Parameters, and the operational characteristics. The MERIS Cal/Val Requirements Report and plan is now complete. This includes calibration requirements, validation of atmospheric correction requirements and the validation of water constituents algorithms. Mike reviewed the following MERIS plans prior to launch.

1997 Identify and select vicarious calibration test sites, detailed plan for VC, prepare airborne campaign, prepare data sets from MOS/OCTS/ in-situ, and simulation studies for Case 1 and 2 waters.

1998 analysis of variability of optical properties and aircraft campaign for case 2 waters, cloud, vegetation, and VC sites.

1999 evaluate campaign results and fine-tune calibration algorithms.

Major questions for the IVOS groups to consider:

1. Where do we stand with respect to the design/definition of a coordinated cal/val strategy for large scale optical sensors?

2. What is the most commonly atmospheric transfer procedure used and what could be the means of translating different correction procedures (between different sensor data sets and consequently make products from different sensors compatible?

3. What Solar Irradiance profile shall we use? There are currently different values being used in the community.


Chris asked if the atmospheric correction issue can't be addressed by the International Radiation Commission? Rao says not, due in part to the proliferation of available RT programs. The key seems to be that investigators should clearly document what RT code was used and, and importantly, what input parameters (spectra etc) are used.

Mike also presented information from the Atmospheric Chemistry Validation Team (ACTV) (E. Attema). They have been working with GOME, MIPAS, GOMOS and Sciamachy. They currently have actions to compile an inventory of validation methods, select a data centre and informatics infrastructure, and to identify likely participants. Plans include:

Feb 97 identification of ACTV members

Summer 97 plenary ACTV meeting

Summer 98 rehearsal campaign

Autumn 99 Envisat commissioning


Chris Mutlow noted that MERIS/ATSR-2 and AATSR should be included as significant parts of the cal/val plans.

Giancarlo Maracci - Vegetation Programme

Giancarlo presented an overview of the VEGETATION instrument characteristics including a brief description of the on-board calibration for the vegetation monitor. Additional general information is available at http://www-vegetation.cst.cnes.fr:8050/. A launch is scheduled for the second half of 1998.

Chris Mutlow - AATSR validation

AATSR will be tied to the same calibration sources as the earlier instruments (ATSR and ATSR-2). The AATSR would be going into the Thermal-Vacuum test chamber soon.

Strategy for Cal/Val of Large Scale Optical Sensors

The chairman suggested that one option to follow would be the method of IOCCG as the inclusion of this activity in IVOS may be too big a task to handle efficiently. Alan Belward stated that this should stay in IVOS because the people who are key to this coordination should be involved in IVOS. Chris Mutlow indicated that the list of attendees may be slightly different, but the work could take place in conjunction with IVOS. Several people agreed that a good first step would be to work on an intercomparison and a coordinated calibration effort over a selected site and the Egyptian (Libyan) desert appeared to be a good candidate. Participants would be asked to bring data samples and actually work through the intercomparison during the next IVOS meeting; this may preempt work on an IVOS data set.

It was also noted that two geostationary satellites cover the Libyan Desert Test Site. Chris will identify people who need to be contacted in order to select a time period, and set up the task. The assumption is that the site will be the Libyan Desert (21-23N and 28-29E) and TOA radiances will be investigated. Guiseppe Zibordi offered to gather a coincident MOS, OCTS, and in-situ data for a coordinated validation effort. Mike Rast noted that this exercise (pilot project) should be viewed as a first step in developing a coordinated cal/val strategy. In addition, the information about RT procedures should be spelled out clearly and used in the intercalibration exercise in order to better identify the specific information which should be requested in the future. Klaus-Dieter Rockwitz noted that an atmospheric instrument group (in ESA) could be asked to develop a strategic plan for calibration and validation and report provide this as input to IVOS.

Strategic Plan

IVOS plans: these should be updated before the next meeting. Alan noted that some other mechanism may be used for the ``living document'' which describes the WGCV activities.

Recommendations to WGCV

Recommendations will be held over until the next subgroup meeting as this will take place before the next plenary.

Action Items

ACTION IVOS-7-1 IVOS members to notify WGCV secretariat of future campaigns.

ACTION IVOS-7-2 Identified members to give details of the following test sites to IVOS NASA representative (J Butler ?) with copies to go to the WGCV secretariat.

ACTION IVOS-7-2-1 P.Slater & S. Biggar. USA ground sites - White Sands, Lunar Lake, Railroad Playa, Ivanpah Playa, Lake Tahoe.

ACTION IVOS-7-2-2 Zhimin Zhang. Dun Huang, Qing Hai Lake.

ACTION IVOS-7-2-3 I. Barton. Hay, Amburla, Strezlecki Desert.

ACTION IVOS-7-2-4 F Adragna. La Crau, Spanish sites.

ACTION IVOS-7-2-5 N. Rao. Libyan Desert.

ACTION IVOS-7-2-6 G. Zibordi. MOBY, Venice Tower, PlyMBODy.

ACTION IVOS-7-2-7 H. Oaku. Japan Sea ocean colour site.

ACTION IVOS-7-2-8 C. Mutlow. Mutsu Bay, Japan.

ACTION IVOS-7-2-9 I. Barton. Australian SST sites.

ACTION IVOS-7-2-10 C. Mutlow. Sudofex.

ACTION IVOS-7-3 I Barton. To contact the NASA IVOS representative (J.Butler ??) with details on the IVOS activities and the importance of test site information.

ACTION IVOS-7-4 NASA representative. To place test site information supplied through ACTION IVOS-7-2 the WWW. Rao suggested that IVOS should confirm that J Butler is the NASA representative on IVOS and that he should be encouraged to attend the meetings.

ACTION IVOS-7-5 C. Mutlow to pass on details of next meeting to IVOS sub-group.

ACTION IVOS-7-6 B. Guenther. To compile reference list on on-board calibration.

ACTION IVOS-7-7 M. Rast. To clarify the status of Solar Irradiance data and activities.

ACTION IVOS-7-8 C. Mutlow. To coordinate the Libyan (North African) Desert site validation exercise.

ACTION IVOS-7-9 B. Guenther. To supply IVOS Chair and the WGCV Secretariat a copy of CEOS/GCOS report from the 1995 Arlington meeting. (Action remaining from WGCV9).

ACTION IVOS-7-10 M. Rast. To circulate cal/val plans and studies when available.

ACTION IVOS-7-11 N. Fox. To communicate to IVOS Chair and WGCV Secretariat a key reference list for NPL's new instrument calibration techniques.

ACTION IVOS-7-12 I. Barton. To email IVOS address list to M. Rast.

ACTION IVOS-7-13 I. Barton. To update the IVOS component of the WGCV 3-year plan and forward to WGCV Chair.

ACTION IVOS-7-14 I. Barton. To compile an IVOS bibliography and forward to WGCV Secretariat.

Next Meeting

The Shanghai Institute of Technical Physics has offered to host the next WGCV meeting in China. IVOS members unanimously expressed the wish to hold the next IVOS meeting during the two days preceding this meeting. There were two time constraints that should be considered in setting these dates.

1. The IGARSS meeting - Aug 4-8 in Singapore.

2. NOAA-K will be launched in mid-August which may impact the NASA and NOAA folks' ability to participate.


The new IVOS Chair would circulate the dates and details of the next meeting as soon as they were available.

Close

The chairman thanked DLR and DARA for co-hosting the meeting and thought that it had been a good meeting. He was hopeful that by the next meeting there would be a substantial increase in the information on test sites that was available on the WWW and that the Libyan Desert exercise would be a start in developing closer collaboration between space agencies in cal/val activities. The meeting closed at 5 pm.

Appendix

ATTENDEES


Name


Institute


Facsimile


Email

Evert Attema ESA +31 7 1565 5675 eattema@estec.esa.nl
Ian Barton (Chair) CSIRO +61 3 6232 5123 ijb@ml.csiro.au
Alan Belward JRC/SAI +39 3 3278 9536 alan.belward@jrc.it
Nigel Fox NPL, UK +44 18 19436935 npf@newton.npl.co.uk
Dennis Helder EROS DC, USGS +1 605 688 5880 helderd@ng.sdstate.edu
Charlie Hersom ISTS Canada +1 416 665 1815 hersom@isl.ists.ca
Mary James EOS Ltd +44 12 5271 2552 maryj@eos.co.uk
Kiran Kumar ISRO +91 7 9675 1752 kiran@sac.ernet.in
Giancarlo Maracci JRC/SAI +39 3 3278 5461 giancarlo.maracci@jrc.it
Garth Morgan ACTE +61 8 8302 5344 garth.morgan@unisa.edu.au
Chris Mutlow RAL, UK +44 12 3544 6525 c.t.mutlow@rl.ac.uk
Wolfgang Noack DLR +49 81 5328 1446 noack@dfd.dlr.de
Hiromi Oaku NASDA +81 3 3224 7052 oaku@eorc.nasda.go.jp
Lasse Pettersson NERSC/NSL +47 5520 0050 lasse.pettersson@nrsc.no
C R Nagaraja Rao NOAA +1 301 763 8136 nrao@nesdis.noaa.gov
Michael Rast ESA +31 7 1565 5675 mrast@jw.estec.esa.nl
David Robinson NPL, UK +44 18 1943 6755 dwr1@newton.npl.co.uk
Klaus-Dieter Rockwitz DARA +49 2 2844 7700
Philip Slater U. of Arizona +1 52 0621 8292 philip.slater@opt-sci.arizona.edu
Phil Teillet CCRS +1 613 947 1383 teillet@ccrs.nrcan.gc.ca
Stephen Tjemkes EUMETSAT tjemkes@eumetsat.de
Giuseppe Zibordi JRC/SAI +39 3 3278 5902 giuseppe.zibordi@jrc.it

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