GRWG/VNSG Web Meeting 2016-08-30

GSICS Web Meeting on Lunar Calibration

Agenda

1. EUMETSAT (S. Wagner, B. Viticchie, T. Hewison): Status of GIRO + GLOD licencing
2. USGS (T. Stone): Status of the on-going activities at USGS + plans for the coming months
3. Earth Space Solution (M. Krijger and R. Snel): Preliminary SCIAMACHY Lunar observations as intercalibration source
4. CMA (S. Hu and L. Chen): Preliminary results from the on-ground lunar observation campaigns CMA in 2015-2016
5. NOAA (F. Yu): latest results on the NOAA developments regarding lunar calibration: Lunar Radiance Site Selection
6. IMD (Ashim Kumar Mitra): INSAT-3D Calibration Using Moon
7. 12:30 UTC Discussion: Second Lunar Calibration Workshop in 2017

Attendees

Guest Chair: Sebastien Wagner (EUMETSAT)

AIST: Toru Kouyama

CMA: Lin Chen, Ronghua Wu, Lu Zhang, Yang Wang, Scott Hu (part of the meeting)

CNES: --

Earth Space Solutions (company): Matthijs Krijger, Ralph Snell

EUMETSAT: Sebastien Wagner, Tim Hewison, Bartolomeo Viticchie

IMD: Ashim K.Mitra

ISRO: --

JAXA: Yoshihiko Okamura, Hiroshi Murakami

JMA: Arata Okuyama, Masaya Takahashi

KMA: Dohyeong Kim, Hyesook Lee, Minju Goo

NASA: Alex Morgan, Zhipeng Wang, Truman Wilson, Dave Doelling

NIST: --

NOAA: Fangfang Yu, Fred Wu

ROSHYDROMET: --

Universität Hamburg: Martin Burgdorf

USGS: Tom Stone

VITO: Stefan Adriaensen

WMO: --

Summary

1. EUMETSAT (S. Wagner, B. Viticchie, T. Hewison): Status of GIRO + GLOD licensing

Ancillary data all cleared for distribution.

Wanted details of composite spectrum - ID numbers of spectra and weights now provided by Tom Stone - will be provided to users.

License agreement now drafted - in review. Will be sent out to all signatories by end Sept 2016.

Infrastructure - will be hosted by EUMETSAT

Routines previously taken from Numerical Recipes have now been recoded in C. Seb also showed the results of the comparisons of output radiances before and after recoding - which are very tiny, almost at machine precision. Tom is satisfied that the differences are much less than the uncertainties in the ROLO model.

Still need to document traceability of GIRO to ROLO, and define a benchmark for systematic testing of GIRO implementation. Will be done in the coming months.

Seb clarified that GIRO license agreement refers to representative data from each instrument - not necessarily data from commissioning, whose distribution may be subject to restrictions.

2. USGS (T. Stone): Status of the on-going activities at USGS + plans for the coming months

Tom provided an overview of the new datasets that would need to be acquired to substantially improve the ROLO model. The programme currently undertaken by NIST offers hope of providing a suitable dataset. NASA’s ARCSTONE cubesat mission is also highly promising. However, Tom first plans to do a data quality check against the original ROLO data, which could be reprocessed to refit the model. This would be based on a reformulated libration terms, adding a wavelength dependence (based on evidence from VIIRS dataset). Tom explained that this work still requires funding support - although he is already funded to assess the uncertainties in the ROLO model. When asked, Tom explained that he expects to have completed the reprocessing and uncertainty assessment of the ROLO dataset by the time of a 2nd Lunar Calibration Workshop in second half of 2017.

3. Earth Space Solutions (M. Krijger and R. Snel): Validation of the SBAF using lunar hyperspectral measurements

As presented at the GSICS User Workshop in August 2016.

Analysed lunar observations taken with SCIAMACHY over the lifetime of ENVISAT - and in particular during dedicated lunar observing period - are being used in a study for EUMETSAT to validate the SBAFs derived from GIRO. Matthijs also pointed out that GIRO can used with the lunar observations to correct for the drift in SCIAMACHY’s UV band, and for its scan-angle dependence. Tom was concerned about the ability of GIRO to generate reliable high spectral resolution reflectance signals - however, Ralph confirmed that no such features had observed in the comparison of SCIAMACHY with GIRO (although he had previously observed spectral problems in the NIR band using his own implementation of ROLO). Maybe some more analysis might be required on those aspects. Some features in the 950nm region overlap between different detector technologies were discussed, which could be followed up at the next Lunar Calibration Workshop.

4. CMA (S. Hu and L. Chen): Preliminary results from the on-ground lunar observation campaigns CMA carried on in 2015-2016

From Lijiang high altitude site (>3000m) in arid climate with frequent clear skies from Dec 2015 to Feb 2016. 10 days selected for further study and comparison with GIRO and MT2009 models. Atmospheric corrections, based on radiosonde profiles and lidar AOD retrievals as input to MODTRAN RTM - however, these are believed to introduce biases in the corrected observations compared to the models. Tom mentioned that the MT2009 model was developed with the specific purpose of quantifying the top-of-atmosphere spectral irradiance from the Moon and to make a quantitative use of NPP-VIIRS Day-Night band observations acquired on the night side of Earth, illuminated by the Moon. It was not intended to be a radiometric calibration reference, and the paper (TGRS 47, 2316(2009)) lists several limitations of this model. The most important are: no distinction of waxing and waning phases, no libration dependence, and no accounting for the opposition effect.

Lin confirmed that some of the data should be available to the Lunar Calibration community - would make a useful theme for the next workshop. Ongoing observations are planned, following further instrument improvements. Furthermore, it may be possible to host instruments from international partners at the Lijiang site.

5. NOAA (F. Yu): latest results on the NOAA developments regarding lunar calibration: Lunar Radiance Site Selection

Postponed until next web meeting

6. IMD (Ashim Kumar Mitra): INSAT-3D Calibration Using Moon

Postponed until next web meeting

7. Discussion: Second Lunar Calibration Workshop in 2017

Discussion on the organisation of a second lunar calibration workshop next year. CMA has kindly offered to host and organise such a workshop in the second half of 2017 in China. So we should think about the topics to be addressed during that workshop and how we want to address them. The first workshop we had in Darmstadt was rather straightforward: there was a needed to converge on an standard and common tool to achieve lunar calibration and so we did with the GIRO. So we had the possibility to have a real workshop (as opposed to mini-conference), with some practical work to be done in preparation of the workshop and during the workshop. This time, it is likely to be different. For the moment, and after some preliminary interaction with Scott Hu (CMA) and Tom Stone (USGS), the items we could address during the second workshop are:

• Measurements, Moon observations: the focus would be on measurement/observation campaigns such as the one that CMA did and on the outcome of those campaigns (dataset, analysis, new model, better characterisation of existing model, etc.). This could include also the latest news from the SELENE mission. Maybe some experiments using CIMEL? CMA observations include CIMEL measurements. So we could also may be discuss how those measurements could be used...
• Improvement of the ROLO/GIRO: what are the activities that could benefit to the ROLO/GIRO to improve it? What has been done (defining reference benchmark for model validation purposes, improvement of the libration in the model, etc.)? What is the status on the ROLO/GIRO (science, infrastructure, operational use, etc.)
• Inter-calibration using the Moon: from the GSICS standpoint, what are the news on inter-calibration, SBAF validation, etc. This would be related to the proposals CNES and EUMETSAT made at the last annual meeting for inter-calibration using the Moon. This item would also include some potential outcome of Masaya Takahashi's visit at EUMETSAT (we could use AHI data to resolve some aspects of the inter-calibration).
• Alternative methods: here I think for instance of the effort undertaken by NOAA and JAXA with the radiance maps of the Moon and their use for absolute calibration using Moon sites as invariant targets. New lunar references, etc. Is CMA working on a new model for instance?
• How to interpret GIRO/ROLO results
  - definition of common tools to analyse inputs and outputs?
• How to address ROLO-GIRO traceability?
• How to address oversampling factors?
• Commissioning/Validation datasets as part of GLOD?

Discussions

How long? Probably 4 days - maybe 5 if many topics to be discussed.

When? CMA does not have particular constraints on the time frame for organising the event in the second half of 2017. However, NOAA mentioned some issues with their budget calendar and would prefer to have the workshop after September or October. In order to prepare the workshop, the later the better if there are many topics. Similarly to the first workshop, a poll will be organised with proposed dates.

Where? China - but specific location to be confirmed.

Common Tools? Some support, but more likely, common procedures for analysis.

Round Table Review of Workshop Priorities (by agency alphabetical order) (new items in red)

• AIST: inter-calibration to link satellites with very different spatial resolution, and assessing uncertainties in ROLO.
• CMA: would like to learn from Himawari-8/AHI data, if it could be made available to the Lunar Calibration community - JMA are planning to share some AHI lunar data this autumn. CMA is interested in improvements of ROLO/GIRO by combining satellite and ground-based observations (and defining some recommendations on how to combine those multiple sources of information), as well as inter-calibration of operational sensors against AHI.
• Earth Space Solution (company): inter-calibration (also for future missions) + polarisation of Moon (especially phase dependence), future ROLO improvements (including absolute accuracy).
• EUMETSAT: interest in all cited topics (measurements, ROLO/GIRO improvements, inter-calibration and alternative methods). Additionally, interest in polarisation in order to assess the level of uncertainties introduced by instrument polarisation sensitivity, and in post-launch characterisation of MTF using the Moon for sharp edges.
• IMD: share experiences with applying GIRO to GEO imagers and develop inter-calibration methods.
• JAXA: Improvement of ROLO & GIRO and how to share results of cross-calibration
  + Yoshihiko: interested in the inter-calibration. The improvement of the lunar model and GIRO by the new measurement campaign is an important topic.
• JMA: Assume inter-calibration covered by GSICS, so workshop should focus more on analysis + radiance model. But inter-calibration is in any case of interest for JMA.
• KMA: inter-calibration development, sharing experiences with 5 years of lunar observations, improvement of the ROLO/GIRO absolute accuracy.
• NASA: Truman Wilson - improvements to ROLO+GIRO and development of inter-calibration. Zhipeng Wang will be able to provide updated observations from MODIS and VIIRS to GLOD and is working on application of lunar calibration to IR channels, but would like to learn more about radiance modelling. MTF characterisation.
• NOAA: Lunar Radiance Model validation and ROLO/GIRO uncertainties + polarisation. Also of particular interest, model improvements - both irradiance and radiance (joint venture), application to ABI and comparison with AHI.
• University of Hamburg (Martin Burgdorf) inter-calibration at microwave wavelengths, observing campaigns in microwave - application of lunar calibration for FIDUCEO
• USGS: Methods on processing data from each instrument to build a common consensus on absolute lunar irradiance
• VITO: Plans to apply GIRO to Proba-V and provision of data to GLOD. Would like to develop inter-calibration based on this.

Outcome

Seb will set up a Doodle poll to select the workshop date and a follow-up web meeting in a few weeks to firm up details topics for workshop and to ask for volunteers to lead each topic. The deferred presentations will also be presented there.