IMOS - Satellite Remote Sensing - Radiometry Community of Practice document
Updated: 2026-10-07
This Integrated Marine Observing System (IMOS) radiometry community-of-practice document summarises important elements of community-agreed, internationally used, protocols for measurement of radiometric quantities in open ocean, coastal and inland waters (from instrument deployment to data handling protocols).
Data
- Ocean Colour page on IMOS website
- IMOS radiometry community-of-practice document - Version 1.0
- Full metadata link
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- {"title":"IMOS - Satellite Remote Sensing Facility","recordAbstract":"The aim of the Satellite Remote Sensing facility is to provide access to a range of satellite derived marine data products covering the Australian region.\n\nThe facility has established a new X-Band reception facility at the Australian Institute of Marine Research near Townsville and upgraded the Tasmanian Earth Resource Satellite Station near Hobart. \n\nThese stations and facilities in Perth, Melbourne, Alice Springs and Darwin form a network supplying the facility with near real-time data. These data are combined and processed to a number of products which are placed on disk storage systems in Melbourne, Canberra and Perth.\n\nThe Bureau of Meteorology has developed a sea surface temperature (SST) product in GHRSST-PP (http://ghrsst-pp.metoffice.com/) L3P format. The Bureau is developing some other SST products including daily and skin SSTs.\nThese new products and some \"ocean colour\" products from MODIS will gradually become available.\n\nScientific users can access these data products are available through OPeNDAP and THREDDS supported technology and also through interfaces provided by AODN and the facility (www.imos.org.au and www.imos.org.au/srs)."}
- {"title":"IMOS - Satellite Remote Sensing - Ocean colour Sub-Facility","recordAbstract":"The Aqua satellite platform carries a MODIS sensor that observes sunlight reflected from within the ocean surface layer at multiple wavelengths. These multi-spectral measurements are used to infer the concentration of chlorophyll-a (Chl-a), most typically due to phytoplankton, present in the water. \n\nThe data are produced from the near real time (nrt) data stream formed by combining data from all the available direct broadcast reception stations in Australia (Alice Springs, Melbourne, Townsville, Perth, Hobart). The data are presented as a sequence of granules, each with a maximum size corresponding to 5 minutes of data, and beginning on UTC-5 minute boundary (eg. 04:05, 04:10, 04:15). The granules have been remapped from satellite projection into a geographic (Latitude/Longitude axes) projection and are formatted as CF-compliant netCDF files. It should be noted that the data are not processed until the definitive spacecraft ephemeris becomes available, usually 12-24 hours after the overpass. This means that the geolocation should be of a uniformly high standard.\n\nThere are multiple retrieval algorithms for estimating Chl-a. These data use the OC3 method recommended by the NASA Ocean Biology Processing Group and implemented in the SeaDAS processing software l2gen. The radiometric sensitivity of the MODIS sensor is evolving continuously during its mission and is being monitored regularly. The SeaDAS software uses tables of calibration coefficients that are updated periodically. From time to time upgrades to the algorithms and thand/or the format of the calibration tables are required, in which case a new version of SeaDAS is released. These data are initially being produced using SeaDAS 6.1, then SeaDAS 6.4 and eventually with SeaDAS 7.x. The data processed with each different version can be distinguished by the digits at the end of the root URL for the data; for example l2oc.nrt.61 is level-2 ocean colour (l2oc), using the near real time (nrt) data stream, produced using SeaDAS 6.1."}
- {"title":"IMOS - Satellite Remote Sensing - Satellite Altimetry Calibration and Validation Sub-Facility","recordAbstract":"Satellite-based altimeters provide fundamental observations of sea surface height that continue to underpin our understanding of the ocean’s role in the Earth’s climate system. Understanding changes in mean sea level at global to regional scales is critical for understanding the response of the ocean to a warming climate – both through the thermal expansion of the ocean and the melting of mountain glaciers and polar ice caps. Sea surface height also provides a lens into ocean dynamic processes at regional to local scales. As with all scientific observations, validation of instrumentation is vital to ensure that measurements are accurate and reliable.\n\nThe IMOS Satellite Altimeter Calibration and Validation Sub-Facility maintains a suite of instrumentation primarily in Bass Strait, providing the only southern hemisphere in situ calibration and validation site that has operated since the launch of the TOPEX/Poseidon mission in 1992. The facility uses Global Navigation Satellite Systems (GNSS) equipped buoys on the ocean surface as well as an array of sub-surface moored oceanographic instrumentation that includes temperature, pressure and salinity sensors and advanced 5-beam acoustic doppler current profilers (ADCPs). Data from this infrastructure is combined to derive a sustained Sea Surface Height (SSH) record that can be directly compared to altimeter measurements. These data provide important contributions to Ocean Surface Topography Science Team (OSTST) and other mission-specific validation teams including those associated with the Sentinel-6 Michael Freilich, Sentinel-3A and 3B, and SWOT missions. For validation of nadir altimeters, the key metric of interest to mission science teams the altimeter absolute bias, the difference between altimeter and in situ measurements of SSH in an absolute reference frame. Analysis of the absolute bias record over time helps ensure data produced from satellite altimeters are accurate and precise on a global scale.\n\nIn addition to the primary site located in Bass Strait, the sub-facility operates some sensors opportunistically at other sites including at the Southern Ocean Flux Station (SOFS) in the Southern Ocean, and at Davies Reef and Yongala in and adjacent to Great Barrier Reef. Data made available from the sub-facility includes:\n\nBass Strait (various locations corresponding to different altimeter comparison points) \n•\tBottom pressure, temperature and salinity (P, T, S)\n•\tWater current (U, V)\n•\tSignificant Wave Height (SWH)\n•\tSea Surface Height (SSH)\n•\tNote different temporal extents and sampling rates are provided on a site-by-site basis deploying on deployments and variable of choice.\n\nSouthern Ocean\n•\tSea Surface Height\n•\tSignificant Wave Height\n•\tNote two different sampling rates are provided. The temporal extent depends on the SOFS deployment.\n\nDavies Reef and Yongala\n•\tBottom pressure, temperature and salinity (P, T, S)\n•\tSea Surface Height\n•\tNote different temporal extents and sampling rates are provided on a site-by-site basis deploying on deployments and variable of choice."}
- {"title":"IMOS - Satellite Remote Sensing - Ocean Colour - Bio Optical Database of Australian Waters","recordAbstract":"Establishment of a bio-optical database of Australian Waters by harvesting all bio-geochemical and bio-optical data from all the IMOS data streams (National Mooring Network, National Reference Stations, Ocean Gliders, Satellite Remote Sensing Ocean Colour - Lucinda Jetty) and from legacy databases (e.g SRFME/WAMSI, Great Barrier Reef Long Term Monitoring Program, Aquafin CRC, Port Hacking transect, Research cruises in the Southern Ocean) it is possible to establish an Australian Database of bio-geochemical and bio-optical data. This Satellite Remote Sensing dataset covers the southern oceans worldwide and Indonesian waters. The Australian Antarctic Division (AAD) and the Australian Institute of Marine Science (AIMS) are providing some of the data to the bio-optical database. This activity aims to collate measurements undertaken prior to the commencement of IMOS by several members of the Australian biological oceanography community. This database is used to assess accuracy of Satellite ocean colour products for current and forthcoming satellite missions for the Australian Waters. The bio-optical database underpins the assessment of ocean colour products in the Australian region (e.g. chlorophyll a concentrations, phytoplankton species composition and primary production). Such a data set is crucial to quantify the uncertainty in the ocean colour products in our region. Further, it is essential to assessing new ocean colour data products generated for the Australian region. The contribution of such a database to international space agencies ensures that the accuracy of global algorithm developed for future sensors will increase for Australian waters as bias towards Northern Hemisphere observation will be reduced. The database contains biooptical data (i.e. HPLC, Chlorophyll by spectrophotometric methods, full spectral absorptions, TSS ) and in situ optical data (Vertical attenuation, water leaving radiance, reflectances, Atmospheric Optical Depth, spectral and single channel absorption and backscattering)."}
- {"title":"IMOS - Satellite Remote Sensing - Surface Waves Sub-Facility","recordAbstract":"The Surface Waves Sub-Facility, part of the Satellite Remote Sensing Facility, will calibrate, collect and distribute ocean surface wave data from current and next-generation satellite missions.\n\nThe Sub-Facility will build Australia’s capability in Satellite Remotely Sensed wave data-streams and deliver global validated, processed wave data streams, with a focused effort in the Australian region. Activities will include:\n\n•\tbuilding on the wave measurements obtained from the Bass Strait altimeter calibration sites for calibration of the current satellite missions in the Australian region,\n•\tusing the Southern Ocean Flux Station to validate wave data in the extreme Southern Ocean wave climate,\n•\tdelivering historical and near-real-time altimeter-derived significant wave heights to the IMOS OceanCurrent Facility, producing daily maps and animations that will be used by researchers and the broader community,\n•\tmanaging the delivery of wind-wave data derived from altimeter and synthetic aperture radar (SAR) satellite platforms to the Australian marine and coastal science community."}
- {"title":"IMOS - Satellite Remote Sensing - Ocean Colour Sub-Facility - Lucinda Jetty Coastal Observatory (LJCO)","recordAbstract":"The Lucinda Jetty Coastal Observatory (LJCO) is located on the end of the 5.8 km long Lucinda Jetty (18.52 S, 146.39 E) in the coastal waters of the Great Barrier Reef World Heritage Area close to the Herbert River Estuary and the Hinchinbrook Channel in Queensland.\n\nThe observatory acquires continuous above and in-water optical measurements with the objective to support satellite ocean colour validation and algorithm development. Data collection and delivery was interrupted in 2011 with tropical cyclone Yasi. Currently, LJCO is the only southern-hemisphere ocean colour validation site integrated into NASA’s AERONET-OC global network of ground-based radiometers and one of a few sites globally that combines the acquisition of both atmospheric and in-water optical measurements. \n\nMounted instruments on the LJCO included:\n- Met Station (Vaisala WXT520)\n- Above-water radiometry\n--- CIMEL SeaPRISM\n--- Satlantic HyperOCR\n--- DALEC instrument (added in mid-2016 for continuous hyper-spectral radiometric measurements)\n-Instrument telemetry\n--- Power supply\n--- UPS\n--- NextG Router\n--- WETLabs DAPCS\n--- PC controller\n--- Automated winch\n- Underwater optics\n--- WETLabs WQM\n--- WETLabs Eco Triplet\n--- WETLabs ac-s\n--- WETLabs BB9\n- Campbell Scientific submersible pressure transducer\n\nThe above-water measurements collected at LJCO compromise of multi-spectral water-leaving radiance and atmospheric observations for retrieving aerosol optical properties using an autonomous CIMEL SeaPRISM radiometer, in addition to hyper-spectral down-welling radiance\nmeasurements using the a Satlantic Hyper-OCR. In mid 2016 continuous hyper-spectral radiometric measurements were added using the DALEC instrument.\n\nThe in-water optical measurements consist of conductivity, temperature, pressure, dissolved oxygen, chlorophyll fluorescence and turbidity using a WETLabs WQM, coloured dissolved organic matter (CDOM) fluorescence using a WETLabs EcoTriplet, as well as particulate and dissolved spectral absorption and attenuation coefficients using a WETLabs AC-S. Further, total backscattering coefficients are measured using a WETLabs BB9 radiometer. \n\nAdditional meteorological and sea state measurements are continuously recorded such as barometric pressure, relative humidity, air emperature, wind speed and direction using a Vaisala WXT520 weather transmitter. Wave height and water temperature are measured with a Campbell Scientific submersible pressure transducer that is used to keep the caged in-water optical instruments at a constant depth.\n\nAll data streams are processed in delayed-mode with automatic quality control applied and made publicly available through the AODN portal; and the data presented here is the daily in-water generated products."}
- {"title":"IMOS - Satellite Remote Sensing - Satellite Sea Surface Temperature (SST) Products Sub-Facility","recordAbstract":"As part of the Integrated Marine Observing System (IMOS), the Australian Bureau of Meteorology produce high-resolution satellite sea surface temperature (SST) products over the Australian region, designed to suit a range of operational and research applications. All these products follow the latest International Group for High Resolution Sea Surface Temperature (GHRSST: www.ghrsst.org) file formats, assisting international data exchange and collaboration.\nThe highest spatial resolution (1 km x 1 km) data from Advanced Very High Resolution Radiometer (AVHRR) sensors on NOAA polar-orbiting satellites can only be obtained through receiving direct broadcast “HRPT” data from the satellite. In Australia, HRPT data is received by a number of agencies (Bureau of Meteorology, Geoscience Australia, AIMS and CSIRO) and consortia (WASTAC and TERSS) at ground-stations located in Darwin, Townsville, Melbourne, Hobart, Perth and Alice Springs and in Antarctica at Casey and Davis Stations.\n\nThe Bureau of Meteorology, in collaboration with CSIRO Marine and Atmospheric Research, is combining raw data from the various ground-stations and producing real-time HRPT AVHRR skin (~ 10 micron depth) SST data files in the GHRSST GDS v2.0 L2P (single swath, geolocated), L3U (single swath, gridded), one and three day daytime/night-time L3C (single sensor, multiple swath, gridded) and one, three and six day daytime/night-time L3S (multiple sensors, multiple swath, gridded) formats. The L2P, L3U, L3C and L3S files for NOAA-15, 17, 18 and 19 satellite data are available through the IMOS FTP server (ftp://aodaac2-cbr.act.csiro.au/imos/GHRSST), IMOS AO-DAAC (http://www.marine.csiro.au/remotesensing/imos/aggregator.html# ) and IMOS Ocean Portal (http://imos.aodn.org.au/webportal/), and will eventually be available through the GHRSST Global Data Assembly Centre (http://ghrsst.jpl.nasa.gov). Archived raw HRPT AVHRR data from Australian and Antarctic ground-stations back to 1992 will be progressively reprocessed into skin SST L2P, L3U, L3C and L3S files and be available to GHRSST and IMOS by June 2013.\nFor the user, there are several advantages to using GHRSST-format SST products. For each SST value the GHRSST files contain a quality level flag (based on proximity to cloud, satellite zenith angle and day/night) and bias and standard deviation error estimates based on 60 day match-ups with drifting buoy SST data. Note that the closer an SST pixel is to cloud, the higher the standard deviation. Therefore, the presence of these quality level flags and error information enable users to tailor the L2P, L3U, L3C or L3S files for their particular research application by trading SST spatial coverage for accuracy and vice versa. Users have the ability to access L3U, L3C and L3S SST products through IMOS OPeNDAP servers, greatly simplifying data access and extraction. Providing real-time HRPT AVHRR SST files in GHRSST-L2P format enables them to be incorporated into global and regional, gap-free, analyses of L2P SST from multiple satellites such as NASA’s G1SST global 1 km daily SST analysis and the Bureau of Meteorology’s daily regional and global SST analyses (RAMSSA and GAMSSA).\nThe new IMOS AVHRR L2P SSTs exhibit approximately 75% the error of the Bureau’s pre-existing HRPT AVHRR level 2 SST data, with standard deviations compared with drifting buoys during night-time of around 0.3°C and during daytime of around 0.4°C for quality level 5 (highest). This significant improvement in accuracy has been achieved by improving cloud clearing and calibration - using regional rather than global drifting buoy SST observations and incorporating a dependence on latitude.\nFor further details on the AVHRR GHRSST products see Paltoglou et al. (2010) (http://imos.org.au/srsdoc.html). Enquiries can be directed to Pallavi Govekar (pallavi.govekar(at)bom.gov.au).\n\n\nAll the IMOS satellite SST products are supplied in GHRSST netCDF format and are either geolocated swath (\"L2P\") files or level 3 composite, gridded files that will have gaps where there were no observations during the specified time period. The various L3U (single swath), L3C (single sensor, multiple swath) and L3S (multiple sensors, multiple swaths) are designed to suit different applications. Some current applications of the various IMOS satellite SST products are:\n\nHRPT AVHRR data:\n\nL2P: Ingestion into optimally interpolated SST analysis systems (eg. RAMSSA, GAMSSA, G1SST, ODYSSEA);\n\nL3U: Calculation of surface ocean currents (IMOS OceanCurrents);\n\nL3C: Estimation of diurnal warming of the surface ocean (GHRSST Tropical Warm Pool Diurnal Variation (TWP+) Project);\n\nL3S: Estimation of likelihood of coral bleaching events (ReefTemp II).\n\nL3P: Legacy 14-day Mosaic AVHRR SST which is a weighted mean SST produced daily from multiple NOAA satellites in a cut-down GHRSST netCDF format. This product is still used in a coral bleaching prediction system run at CMAR. The product is produced using the legacy BoM processing system and is less accurate than the new IMOS L3S product.\n\nGeostationary satellite MTSAT-1R data:\n\nL3U: Hourly, 0.05 deg x 0.05 deg SST used for estimation of the diurnal warming of the surface ocean and validation of diurnal warming models (TWP+ Project)."}
- {"title":"Satellite Remote Sensing-A Satellite SST Products","recordAbstract":"The aim of the Australian Satellite SST L2P Products sub-facility is to provide real-time and reprocessed, high-resolution (1 km and 5 km), locally received, satellite sea surface temperature (SST) data products in the internationally accepted GHRSST L2P and L3P format using new, best practice, processing and calibration methods. The satellite sensors to be used are the AVHRR infrared sensors on the NOAA polar-orbiting satellites, the MODIS infrared sensors on Aqua and Terra and infrared sensors on available geostationary satellites (eg. MTSAT-1R)."}
- {"title":"IMOS - Satellite Remote Sensing - Ocean Colour - Ships of Opportunity - Radiometer Sub-Facility","recordAbstract":"Calibrated DALEC Transect data The Dynamic above water radiance and irradiance collector (DALEC) is a radiometrically calibrated hyperspectral radiometer developed by In situ Marine Optics for autonomous ship based deployment. It contains three Zeiss UV-Vis enhanced spectroradiometers designed to measure near-simultaneous spectral upwelling radiance (Lu), downwelling radiance (Lsky) and downwelling irradiance (Ed). DALEC0001 is deployed on the foremast of the RV Southern Surveyor (VLHJ) and on the RV Solander. Spectra are collected during daylight hours when the ship is at sea subject to suitable sea conditions. Ancillary attitude data for the DALEC included in the dataset are pitch (degrees), pitch standard deviation (degrees), roll (degrees), roll standard deviation (degrees) and gear position (degrees from the bow). The dataset begins July 2011 and is on-going."}
