NET-Sense is the joint NASA ESA Temperature Sensing Experiment. The overall objectives of NET-Sense are related to the proposed future European High Spatio-Temporal Resolution Land Surface Temperature Monitoring (LSTM) satellite mission, which is a candidate future Sentinel satellite. Evapotranspiration is the process by which water is transferred from the land to the atmosphere by evaporation from the soil and other surfaces, and by transpiration from plants. The weather, crop characteristics, agricultural and land management and environmental aspects are all factors that affect levels of evaporation and transpiration, and the ability to map levels of evapotranspiration across agricultural landscapes provides information that is extremely useful in understanding better how much water different plants require in different regions, and how they respond to stresses such as unusually dry periods. The LSTM mission aims to address these types of water, agriculture and food security issues by monitoring the variability of land surface temperature (LST) at the European field scale, from which estimates of evapotranspiration can be mapped. This in turn will provide more robust estimates of field-scale water productivity and support the Copernicus land monitoring service, related European and also Global and international policies as well as downstream applications related to other science areas such as natural hazards and urban climate.
The primary aim of NET-Sense is to help initial work on the LSTM design by collecting unique data over mainly agricultural and urban landscapes in the UK and in continental Europe with highly sophisticated airborne remote sensing systems. These data will be used to aid the LSTM mission design and the specification of the algorithms that will be used to deliver estimates of LST and evapotranspiration from the ‘raw’ LSTM data. For this reason NET-Sense involves flying one of the most sophisticated airborne thermal imaging sensors currently available – the HyTES system designed and built by NASA’s Jet Propulsion Laboratory (JPL). HyTES has never flown in Europe before, but was a key instrument used aid the design of NASA’s ECOsystem Spaceborne Thermal Radiometer Experiment on Space Station ECOSTRESS mission. ECOSTRESS is mounted on the outside of the International Space Station (ISS), and is itself designed also to measure the temperature of plants and use that information to better understand evapotranspiration. NET-Sense is making use of the JPL HyTES capability, alongside UK capabilities in Earth Observation science to collect a unique airborne dataset over a series of landscapes where scientific experiments and data collection is already ongoing with collaborators in the UK and continental Europe.
Copernicus is the European Union’s Earth Observation (EO) Programme, led by the European Commission and examining at our planet and its environment for the ultimate benefit of all European citizens and the wider world. The Copernicus Programme offers comprehensive data and a series of extensive ‘information services’ based on combinations of EO and in situ (non-space) data. The current suite of Copernicus Sentinel satellite missions are at the heart of the Copernicus programme and are developed by the European Space Agency (ESA). Data from these Sentinels feed into the Copernicus Services, which help address challenges such as urbanisation, food security, rising sea levels, diminishing polar ice, natural disasters and, of course, climate change.
Looking to the future, six high-priority candidate satellite missions are currently being studied to address EU policy and gaps in Copernicus user needs, and to expand the current capabilities of the existing Sentinels. One such candidate is the Land Surface Temperature Monitoring (LSTM) mission, which would carry a high spatio-temporal resolution thermal infrared sensor capable of providing detailed observations of land-surface temperature. The mission is in part driven by the priority requirements the agricultural user community have for improving sustainable agricultural productivity at the field-scale in a world of increasing water scarcity and variability. Land-surface temperature measurements and the estimates of evapotranspiration that can be derived from them are some of the key variables required to understand and respond to climate variability, manage water resources for agricultural production, predict droughts and also to address land degradation. Such measurements are also very informative for certain natural hazards such as fires and volcanoes, and for coastal and inland water management as well as urban heat island issues.
HyTES and its Relevance
The Hyperspectral Thermal Emission Spectrometer (HyTES) is an airborne imaging spectrometer designed and built by NASA’s Jet Propulsion Laboratory (JPL), in Pasadena, California. HyTES is one of the world’s most sophisticated airborne thermal imaging instruments, operating in 256 different thermal infrared (TIR) spectral channels (wavelengths) between 7.5 and 12 micrometers in the thermal infrared part of the electromagnetic spectrum. The instrument has very high levels of performance, and requires sophisticated cooling for almost 1 week to provide its very high precision data. Flown on an aircraft, HyTES can provide its data at very high spatial and spectral detail, fare more than can be obtained from Earth orbiting satellites. In this way, the data collected by HyTES can be used to help determine the optimum band positions for the candidate LSTM satellite mission, as well as providing precursor datasets for developing and testing the algorithms that maybe used to turn future LSTM data into accurate maps of land surface temperature and evapotranspiration. By flying HyTES over the sites of existing UK and European experiments, we can also collect data that will be useful to expand the research going on in these areas and in remote sensing research in the TIR in general.
To make the dataset collected even more comprehensive and useful, we will fly HyTES alongside other airborne instruments operated by NERC’s National Center for Earth Observation NCEO) and King’s College London (King’s, which collect hyperspectral data in visible and near/shortwave spectral regions and which can used to identify, for example, the type and condition of the vegetation being imaged by HyTES alongside other properties of the surfaces and regions being targeted for the data acquisitions.
Professor Martin Wooster is a Physicist by training and is Chair of Earth Observation Science within King’s Department of Geography, where he leads the NCEO-King’s team. Wooster is one of four Divisional Director’s within NCEO, and is leading the NETSense campaign planning. He has coordinated many national and international science projects, commonly focused around infrared remote sensing. The NCEO-King’s team are both coordinating the airborne data acquisition side of NETSense, and also providing detailed measurements of many parameters on the ground for validation purposes – for example by installing in situ sensors alongside those of the existing science partners. Professor Wooster’s research profile can be viewed here.