# Presentation: 126604

## AVHRR Data Flow at CCRSPresented by Gunar Fedosejevs

- AVHRR Data Flow at the Canada Centre for Remote Sensing (CCRS) includes satellite data reception, pre-processing, archiving, and enhanced data processing for derived products in support of modelling and global climate research.

## AVHRR Data Flow at CCRS

- CCRS as the official Canadian remote sensing centre has two satellite receiving stations:
- The Prince Albert Satellite Station (PASS)
- The Gatineau Satellite Station (GSS)

## AVHRR Data Flow at CCRS

- PASS has been receiving direct readout High Resolution Picture Transmission (HRPT) data from the Advanced Very High Resolution Radiometer (AVHRR) instrument onboard the National Oceanic and Atmospheric Administration (NOAA) series of satellites since 1973 *(http://www.ccrs.nrcan.gc.ca/ccrs/data/satsens/sats/noaa_e.html).*
- PASS has been receiving HRPT data from NOAA 16 polar-orbiting satellite for ascending (daytime) orbits since April 1, 2001 and descending (night-time) orbits shortly thereafter for most of North America.

## AVHRR Data Flow at CCRS

- NOAA 14 has been drifting into a later orbit where solar contamination has become a problem for thermal calibration.
- The high solar zenith angles from the later orbits also result in unwanted increased bi-directional reflectance distribution function (BRDF) effects in channels 1 and 2.
- CCRS has ceased to acquire NOAA 14 (ascending orbit) data on an operational basis as of March 31, 2001.
- NOAA 14 AVHRR data are still archived by USA to NOAA SAA.
- Users may request acquisition of data by PASS for any operational AVHRR sensor through the CCRS order desk.

## AVHRR Data Flow at CCRS

- Raw Products:
- Satellite Acquisition Services Order Desk
- Canada Centre for Remote Sensing
- 588 Booth Street
- Ottawa, Ontario
- CANADA
- K1A 0Y7
- Tel: (613) 995-4057
- Fax: (613) 992-0285
- Email: orderdesk@ccrs.nrcan.gc.ca

## AVHRR Data Flow at CCRS

- NOAA 15&16 contain the new AVHRR/3 instrument with six spectral channels. Channel 1 (visible), 2 (NIR), 3A (SWIR), 3B (MIR), 4 (TIR), 5 (TIR) have centre wavelengths of 0.65, 0.85, 1.6, 3.6, 10.5, 11.5 um, respectively.
- Satellite data transcription systems were designed to handle 5 channels of the AVHRR/2 onboard NOAA 14 and earlier missions.
- Thus, NOAA 15&16 are programmed to acquire channel 3A during the day (ascending orbit) and channel 3B during the night (descending orbit).

## AVHRR Data Flow at CCRS

- For descending orbits passing over the Canadian arctic, this often results in both channel 3A and 3B data being acquired.
- Channel 3A can be used for cloud/snow/smoke discrimination.
- Technical specifications for NOAA 16 AVHRR/3 can be found in the NOAA KLM User's Guide *(http://www2.ncdc.noaa.gov/docs/klm/index.htm).*

## AVHRR Data Flow at CCRS

- Data Reception at Mont Joli
- NOAA 14 AVHRR HRPT data from ascending daytime orbits were acquired in 1999 and 2000 over Canada's East Coast by the DFO Maurice Lamontagne Institute at Mont Joli for CCRS under a Memorandum of Understanding (MOU).
- Reception of NOAA 16 AVHRR HRPT daytime data at Mont Joli commenced on April 5, 2001 under the same MOU.
-  DFO provides near real-time delivery of AVHRR data as raw and L1B products via ftp to PASS.
- PASS software pre-processes DFO-received data to make them compatible with PASS-received data.

## AVHRR Data Flow at CCRS

- NATAS Data Processing
- HRPT data received at PASS and Mont Joli are processed on the NOAA AVHRR Transcription and Archive System (NATAS) system at PASS *(http://ceocat.ccrs.nrcan.gc.ca/client_acc/guides/avhrr/ch4.html). *
- NATAS raw data products are generated in the Committee on Earth Observations Satellites/Landsat Ground Station Operators Working Group (CEOS/LGSOWG) standard format (refer to STD-TM 90-678F document on Standard Raw AVHRR CCT Image Format Specifications).
- NATAS products are archived on 5-gigabyte 8-mm Exabyte cassettes kept at PASS.

## AVHRR Data Flow at CCRS

- CEOCat Data Catalogue
- All NATAS raw data products can be viewed on the Canadian Earth Observation Catalogue (CEOCat) *(http://ceocat.ccrs.nrcan.gc.ca/cgi-bin/client_acc/ceocate/holdings.phtml).*
- NATAS-generated digital quicklook browse (JPEG) images and Catalogue Update Files (CUFs) are transferred on a daily basis via ftp to a CCRS VAX server at 588 Booth St.
- A batch job initiated daily from the CEOCat server at 615 Booth St. retrieves the data from the VAX server.
- Channels 2, 1 and 1 are displayed as an RGB false colour composite for orbits received from April 1 to October 31 or channel 4 as a B/W image for orbits received in the winter.

## AVHRR Data Flow at CCRS

- CCRS ftp transfer
- Since 2000, CEOS-formatted NATAS raw data .zip files are transferred by ftp from PASS over the internet to a secure CCRS AVHRR ftp site for privileged user access.
- The .zip files for NATAS data are labelled NOAA_16_yyyymmdd_hhmm_nnnnn where nnnnn is the orbit number. The GMT time (hhmm) is for the first scan line when the scene is oriented with north at the top.

## AVHRR Data Flow at CCRS

- CCRS ftp transfer (continued)
- For the descending orbits the jpegs are labeled as 5-minute segments starting with the start orbit time. For the ascending orbit data, the jpegs are labeled as 5-minute segments but starting from the orbit acquisition start time and going forwards (north along the orbit) even though the jpegs are oriented north at the top of the image. The time in the jpeg filename applies to the south end of the images.
- The time in the .zip filename is the acquisition stop time even though the top scan lines in the jpeg may be blank fill.

## AVHRR Data Flow at CCRS

- EMS Data Holdings
- All NATAS data received on the CCRS ftp server are archived on exabyte or DLTs in the Environmental Monitoring Section (EMS) the Applications Division at CCRS
- EMS Data Holdings are applied to various research studies using GeoComp-n (*http://www.ccrs.nrcan.gc.ca/ccrs/rd/ana/geocomp/geocomp_e.html*), ABC3 and other data processing packages in the context of global climate change and vegetation process modelling

## AVHRR Data Flow at CCRS

- MRSC GeoComp-n Data Processing
- The Manitoba Remote Sensing Centre (MRSC) retrieves NATAS data from the CCRS ftp site to be processed on the operational system for Geocoding and Compositing of AVHRR data (GeoComp-n).
- GeoComp-n creates near real time composite products of Canada at 1-km resolution in Lambert Conic Conformal (LCC) projection.
- Canada-wide daily and 10-day composite products containing selected data layers are generated by GeoComp-n for CCRS.
- Alternate composite periods, geographic coverage and data layer selections are available to MRSC subscribers.
- JPEG browse images (using channel 1&2 TOA radiance  and NDVI) and CUFs are sent from MRSC to CEOCat.

## AVHRR Data Flow at CCRS

- GeoComp-n Basic Composite Product Layers:
- TOA radiance and brightness temperature
- TOA reflectance, surface reflectance, BRDF-corrected surface reflectance and associated NDVI
- Satellite and sun zenith/azimuth angles
- Quality control (QC) mask
- Input scene mask
- Pixel count mask
- Relative date
- Residual geometric error mask

## AVHRR Data Flow at CCRS

- GeoComp-n Advanced Composite Product Layers:
- Pixel contamination (CECANT) mask
- Land Surface temperature
- Leaf area index (LAI)
- Instantaneous FPAR
- Daily Mean FPAR
- Instantaneous APAR Daily Total APAR
- Composite Mean APAR
- Fire (hot spot) mask
- PAR albedo

## AVHRR Data Flow at CCRS

- Geocoded and Composite Products:
- Manitoba Remote Sensing Centre
- Roy Dixon
- 1007 Century Street
- Winnipeg, Manitoba
- CANADA
- R3H 0W4
- Tel: (204) 945-6597
- Fax: (204) 945-1365
- Email: rdixon@nr.gov.mb.ca
*WWW: http://www.gov.mb.ca/conservation/geomatics/remote_sensing/index.html*

## AVHRR Data Flow at CCRS

- MRSC Data Transfer to CCRS
- MRSC GeoComp-n products generated for CCRS are sent on exabyte periodically to CCRS.
- In 2000 this data set included virtually all product layers for the daily and 10-day composites for NOAA 14.
-  In 2001/2002 only a subset of product layers were requested for the daily and 10-day composites.
- The 10-day composite radiance data are reprocessed in the

## AVHRR Data Flow at CCRS

- ABC3V2 Data Processing
- At the end of a growing season (April 1- October 31), all 10-day composite data are staged on the ABC3V2 server for processing in the Atmosphere, Bi-directional and Contamination Corrections of CCRS (ABC3) software written in Visual C++ by Rasim Latifovic,
- 	*http://www.ccrs.nrcan.gc.ca/ccrs/rd/apps/landcov/corr/emcorr_e.html*.
- ABC3V2 applies recalibration and other radiometric enhancements. Details can be found in ABC3V2.doc on CCRS anonymous ftp site *ftp://ftp.ccrs.nrcan.gc.ca/ftp/ad/EMS/ABC3Documentation/.** *
- The 1-km resolution output products (.pix files with a file size of 5700 pixels by 4800 lines) are available in LCC projection for model input and derived product generation.

## AVHRR Data Flow at CCRS

- ABC3V2 Data on GeoGratis
- A subset of ABC3V2 product layers from 1993 to 1998 were converted from LCC to geographic (latitude/longitude) projection and archived along with browse and thumbnail images in GeoGratis at URL *http://www.geogratis.gc.ca/frames.html.  *
- These data sets may be searched for on the GeoConnections Discovery Portal at URL *http://ceonet.ccrs.nrcan.gc.ca/.*
- A download of selected dates and product layers of 10-day composite data from GeoGratis is bundled with README.doc and ABC3V2.doc.

## AVHRR Data Flow at CCRS

- ABC3V2 Data on GeoGratis (continued)
- The browse images are 1/10th in size with an RGB assignment of BRDF-corrected NDVI (using only values from 0.9-2.0), ch2 (using only values from 0-0.65) and ch1 (using only values from 0-0.35), respectively.
- The thumbnails are 100 pixels by 42 lines in size before reprojection.
- Retrieval of data sets is based on UNIX tools.
-  If retrieving data files on PC using Winzip, the user must uncheck the "TAR file smart CR/LF conversion" box under Winzip/Options/Configurations/Miscellaneous.

## AVHRR Data Flow at CCRS

- EMS Fire Processing at CCRS
- Batch/perl script/EASI scripts retrieve the NATAS data and processes them in GeoComp-n for fire mapping research by the Fire M3 scientists *(http://fms.nofc.cfs.nrcan.gc.ca/FireM3/).*
- While there are additional benefits of using channel 3A data to the fire modelling, the current hot spot mapping algorithm implemented for NOAA 11 and 14 in GeoComp-n was designed to use channel 3B data.
- A major research effort is ongoing to perform hot spot and smoke detection in NOAA 16 daytime data using channel 3A and hot spot detection in night-time data using the reliable channel 3B data. Channel 3A data can contain a thermal emissive component. Depending on the size and temperature of the fire, pixels can be darker (low reflectivity of burned vegetation) or brighter (hot fire) than for background vegetation.
- Clock corrections for improved accuracy in geocoding are available for NOAA 11, 12, 14, 15 and 16 from NOAA/NESDIS *(http://www.osdpd.noaa.gov/PSB/NAVIGATION/navpage.html).*

## AVHRR Data Flow at CCRS

- EMS Fire Processing at CCRS (continued)
- A mask of false hot spots in night-time composites can be created from permanent thermal sources such as smoke stacks in industrial plants. A similar mask can be built for daytime composites where bright surfaces (e.g. White Sands, New Mexico) are mistaken for smoke in channel 3A.
- Another source of false hot spots is noisy pixels/lines in the raw data. These occur in the NOAA data received by PASS because of data downlink errors when the satellite is low on the horizon. PASS employs a reception mask of zero degrees elevation that can cause bad pixels or calibration sample data. The DFO data acquired at Mont Joli with a mask of 5 degrees contain no bad pixels. These bad pixels must be manually removed as bad line replacement is not envoked for the fire processing in GeoComp-n so as not to miss any hot spots.

## AVHRR Data Flow at CCRS

- GeoComp-n Changes for NOAA 15/16
- GeoComp-n thresholds based on raw counts from the NOAA 15 and NOAA 16 dual gain AVHRR/3 sensor may need to be revised for bad pixel detection, cloud threshold and GCP radiometric threshold; and for any products using raw counts for channels 1 and 2 or computed NDVI.
- GeoComp-n products for NOAA 15 use post-launch time-dependent PWL calibration coefficients based on Tahnk and Coakley ice data.
- GeoComp-n products for NOAA 16 use post-launch time-dependent PWL calibration coefficients based on Heidinger et al. calibration data.
- PWL calibration coefficients are available on CCRS calval web page *http://www.ccrs.nrcan.gc.ca/ccrs/rd/ana/calval/calhome_e.html. *
- A new set of BRDF correction coefficients must be created from a full season of data.
- New product algorithm coefficients specific to NOAA 16 need to be derived because of spectral band differences between NOAA satellites.

## AVHRR Data Flow at CCRS

- AVHRR SST Product
- While Geocomp-n and ABC3V2 can generate land surface temperature (LST) products; CCRS doesn't have an operational sea surface temperature (SST) product. PCI does provide limited support for the SST product in XPACE computed from NOAA 9, 12 and 14 data. The PCI model NOAA_SST.mod was built at CCRS to compute SST for NOAA 9, 11, 12 and 14 and will run in PCI V6.3.

## AVHRR Data Flow at CCRS

- NATAS Historical Data
- CCRS plans are to retrieve 1993-1998 NATAS data from the PASS archive to process through Geocomp-n and ABC3V2.
- PASS is recovering historical NOAA data (<1993) from HDDT and creating a NATAS exabyte archive. The NATAS data are sent to the CCRS AVHRR ftp site as zip files. The browse images and CUFs are sent to CEOCat.
- NOAA data from 1990-1993 with almost complete seasonal coverage are now in CEOCat and the EMS Data Holdings.
- In support of the 1-km global mapping initiative by the USGS EROS Data Center in Sioux Falls, Dakota, year-round acquisition of NOAA 11 and 14 data occurred from April 1992 until October 1997 notwithstanding the data gap between the demise of NOAA 11 in September 1994 and the start-up of NOAA 14 in March 1995 (?).
- The data going back to 1983 are much sparser; but all 10-bit historical data will be archived in CEOCat in time.

## AVHRR Data Flow at CCRS

- AVHRR Space Counts
- Instead of assuming that the calibration offsets (based on pre-launch values for NOAA 15 and 16) as specified in the GeoComp-n radiometric calibration file are the correct ones; the space counts or offset can be read directly from the raw image files generated by NATAS.
- GeoComp-n doesn't retrieve space counts for the non-thermal channels for inclusion in the PCIDSK metadata.
- A Perl script was created to extract the space counts from the suffix (calibration sample) data in the NATAS image file and write them to a text file. The space count records were imported into an Excel file to view the time-dependent behaviour.

## AVHRR Data Flow at CCRS

- AVHRR Solar Contamination
- As NOAA satellites drift into a later orbit, the sun impinges on the AVHRR instrument for part of the orbit, which results in thermal fluxes in the blackbody cavity that affect the PRT readings of the blackbody temperature. The rapidly changing thermal calibration coefficients can result in brightness temperature errors on the order of several degrees Kelvin.
- Trishchenko, A.P., Z. Li. 2001. A method for the correction of AVHRR onboard IR calibration in the event of short term radiative contamination. *IJRS*, vol. 22, no. 17, pp. 3619-3624.
- Trishchenko, A.P. 2002. Removing unwanted fluctuations in the AVHRR thermal calibration data using robust techniques. Journal of Atmospheric and Oceanic Technology (submitted).
- Trishchenko, A.P., G. Fedosejevs, Z. Li and J. Cihlar. 2002. Trends and uncertainties in thermal calibration of AVHRR/NOAA-9 to 16. Journal of Geophysical Research: Atmospheres (submitted).

## AVHRR Data Flow at CCRS

- NDVI Spectral Conversion
- Alex Trichtchenko wrote a journal article describing the spectral dependency of NDVI between NOAA satellites, which included empirical fits between NOAA 14 TOA NDVI values and those from other NOAA satellites. Models that were created for NOAA 14 need to apply a spectral conversion to NOAA 16 data. The spectral conversion is target reflectance dependent.
- Reference:
- Trishchenko, A.P., J. Cihlar, Z. Li. 2002. Effects of spectral response function on surface reflectance and NDVI measured with moderate resolution satellite sensors. *Remote Sensing of Environment* , vol. 81, pp. 1-18.

## AVHRR Data Flow at CCRS

## AVHRR Data Flow at CCRS

## AVHRR Data Flow at CCRS

## Maximal detectable temperature in ch.3B

## Maximal detectable temperatures for NOAA-14  (HRPT scenes from PASS)

## Conclusions

- CCRS provides complete support for NOAA AVHRR data to users
- Web access to quick look images
- COFUR access to raw data
- Near real-time access to composite data by subscription
- Web access to free historical enhanced data

## AVHRR Data Flow at CCRS

- References:
- Adair, M., J. Cihlar, B. Park, G. Fedosejevs, A. Erickson, R. Keeping, D. Stanley, and P. Hurlburt. 2001. GeoComp - n, an advanced system for generating products from coarse and medium resolution optical satellite data. Part 1: System characterization. *Canadian Journal of Remote Sensing*, vol. 28, no. 1, pp. 1-20.
- Cihlar, J., J. Chen, Z. Li, G. Fedosejevs, M. Adair, W. Park, R. Fraser, A. Trishchenko, B. Guindon, and D. Stanley. 2001. GeoComp-n, an advanced system for the processing of coarse and medium resolution satellite data. Part 2: biophysical products for the northern ecosystem. *Canadian Journal of Remote Sensing*, vol. 28, no. 1, pp. 21-44.
- Cihlar, J., Latifovic, R., Chen, J., Trishchenko, A., Du, Y., Fedosejevs, G., and Guindon, B. 2002. Systematic corrections of AVHRR image composites for temporal studies. *Remote Sensing of Environment* (in press).

## Contact

- Gunar Fedosejevs
- Data Acquisition Division
- Canada Centre for Remote Sensing
- 588 Booth Street
- Ottawa, Ontario, Canada K1A 0Y7
- E-mail: Gunar.fedosejevs@ccrs.nrcan.gc.ca
- URL: http://www.ccrs.nrcan.gc.ca/ccrs/