SHIFT: HyTES L2 Geolocated Land Surface Temperature and Emissivity, March 23 2022

This dataset holds Level 2 (L2) data for surface emissivity and land surface temperature (LST) collected by the Hyperspectral Thermal Emission Spectrometer (HyTES) instrument. This imagery was acquired as part of the Surface Biology and Geology High-Frequency Time Series (SHIFT) campaign on March 23, 2022. The SHIFT campaign generated precise, high-frequency data on plant communities for nearly 1,656 square kilometers across Santa Barbara County, California, US, and the nearby ocean. HyTES is a compact image spectrometer that acquires data in 256 spectral bands between 7.5 and 12 micrometers; it was deployed on a Twin Otter aircraft. The SHIFT campaign sought to demonstrate the joint use of both VSWIR and thermal infrared (TIR) data. TIR data are used to measure land surface temperature (LST), which informs models of water flux from land surface through processes such as evapotranspiration. LST is sensitive to solar heat gains and local cooling effects due to evaporative cooling. The HyTES instrument measures TIR radiances that can be used to derive LST, emissivity and Level 3 products such as latent heat flux and detection of air pollution sources. The HyTES data are provided in HDF5 format and include 91 flight scenes. In addition, overlay images for emissivity and LST are provided in compressed Keyhole Markup Language (KMZ) along with a quicklook image.

This dataset includes 455 files: 91 data files in HDF-5 format, 182 files in compressed Keyhole Markup Language (KMZ), and 182 quicklook images in Portable Network Graphics (PNG) format.

This dataset holds Level 2 (L2) data for surface emissivity and land surface temperature (LST) collected by the Hyperspectral Thermal Emission Spectrometer (HyTES) instrument. This imagery was acquired as part of the Surface Biology and Geology High-Frequency Time Series (SHIFT) campaign on March 23, 2022. The SHIFT campaign generated precise, high-frequency data on plant communities for nearly 1,656 square kilometers across Santa Barbara County, California, US, and the nearby ocean. HyTES is a compact image spectrometer that acquires data in 256 spectral bands between 7.5 and 12 micrometers; it was deployed on a Twin Otter aircraft. The SHIFT campaign sought to demonstrate the joint use of both VSWIR and thermal infrared (TIR) data. TIR data are used to measure land surface temperature (LST), which informs models of water flux from land surface through processes such as evapotranspiration. LST is sensitive to solar heat gains and local cooling effects due to evaporative cooling. The HyTES instrument measures TIR radiances that can be used to derive LST, emissivity and Level 3 products such as latent heat flux and detection of air pollution sources. The HyTES data are provided in HDF5 format and include 91 flight scenes. In addition, overlay images for emissivity and LST are provided in compressed Keyhole Markup Language (KMZ) along with a quicklook image.

Project:  Surface Biology and Geology High-Frequency Time Series (SHIFT)

The Surface Biology and Geology (SBG) High Frequency Time Series (SHIFT) was an airborne and field campaign during February to May, 2022, with a follow up activity for one week in September, in support of NASA's SBG mission. Its study area included a 640-square-mile (1,656-square-kilometer) area in Santa Barbara County and the coastal Pacific waters. The primary goal of the SHIFT campaign was to collect a repeated dense time series of airborne Visible to ShortWave Infrared (VSWIR) airborne imaging spectroscopy data with coincident field measurements in both inland terrestrial and coastal aquatic areas, supported in part by a broad team of research collaborators at academic institutions. The SHIFT campaign leveraged NASA's Airborne Visible-Infrared Imaging Spectrometer-Next Generation (AVIRIS-NG) facility instrument to collect approximately weekly VSWIR imagery across the study area. The SHIFT campaign 1) enables the NASA SBG team to conduct traceability analyses related to the science value of VSWIR revisit without relying on multispectral proxies, 2) enables testing algorithms for consistent performance over seasonal time scales and end-to-end workflows including community distribution, and 3) provides early adoption test cases to SHIFT application users and incubate relationships with basic and applied science partners at the University of California Santa Barbara Sedgwick Reserve and The Nature Conservancy's Jack and Laura Dangermond Preserve.

Related Datasets

Rivera, G., W.R. Johnson, R.J. Freepartner, B. Eng, and S.J. Hook. 2023. SHIFT: HyTES L1 Brightness Temperature, March 23 2022. ORNL DAAC, Oak Ridge, Tennessee, USA. https://doi.org/10.3334/ORNLDAAC/2245

Hulley, G.C., R.J. Freepartner, and S. J. Hook. 2023. SHIFT: HyTES L3 Geolocated Multispecies Gas Products, March 23 2022. ORNL DAAC, Oak Ridge, Tennessee, USA. https://doi.org/10.3334/ORNLDAAC/2247

Acknowledgement

SHIFT is jointly led by NASA’s Jet Propulsion Laboratory, The Nature Conservancy, and the University of California, Santa Barbara (UCSB).

Spatial Coverage: Santa Barbara County, California and nearby Pacific Ocean

Spatial Resolution: Variable by flight segment; generally between 3 to 6 meters.

Temporal Coverage: 2022-03-23 

Temporal Resolution: Multiple flights over study area on a single day

Study Area: (All latitudes and longitudes given in decimal degrees) 

Study Area	Westernmost Longitude	Easternmost Longitude	Northernmost Latitude	Southernmost Latitude
Santa Barbara County, California and nearby Pacific Ocean	-120.604	-118.784	34.886	33.180

Data File Information

This dataset includes 455 files: 91 data files in HDF-5 format, 182 files in compressed Keyhole Markup Language (KMZ), and 182 quicklook images in Portable Network Graphics (PNG) format.

There are 91 flight scenes with five files for each scene.

The naming convention for most data files is <date>t<time>_<location>_<product >_<build ID>_<version ID>.<file format type>

• <date> = date in YYYYMMDD
• <time> = time at beginning of data acquisition in HHMMSS.  All dates and times are in UTC.
• <location> = short text description of the scene (e.g., "VenturaCA", "SantaBarbaraCA", "PtConceptionCA")
• <product> = Level 2 product: "L2-emis" = emissivity and "L2-LST" = land surface temperature
• <build ID> = software build ID used (e.g., "B103")
• <version ID> = the incremental version the scene has been run for that build ID (e.g., "V01")
• <file format> = file format types: "hdf5" = HDF5, ""kmz" = compressed Keyhole Markup Language, and "png" = Portable Network Graphics image.

The HDF5 files hold datasets including emissivity and land surface temperature (LST) measurements.  These data are organized in a matrix with three dimensions: lines x samples x bands. The lines are pixels along the flight path, and the number of lines varies with the period of data acquisition. The samples (n = 512) are pixels arranged perpendicular to the flight path. For emissivity, there are 202 or 265 wavelength bands (Table 1). There is a single band for LST. The emissivity and LST data are not projected but geolocation information for each pixel is included in the pixel_geolocation dataset in the HDF (Table 1).

The KMZ files hold an overlay images of emissivity and LST for the flight scenes that are viewable in Google Earth.
The PNG files are quicklook images of emissivity and LST for the respective flight scene.

Table 1. Datasets in HDF data files.

Dataset	Description
ISAC_Path_Rad	Atmospheric scattered radiance. One value per 256 sensor bands.
ISAC_Skydown_Rad	Downwelling sky radiance. One value per 256 sensor bands.
L2_Emissivity	Emissivity in lines x samples x bands matrix.  Bands = 202 covering wavelenghts of 8 to 11.5 µm.
L2_Emissivity_Wavelengths	Wavelengths in µm for each band (n=202) for L2_Emissivity data.
L2_Emissivity_PC	Emissivity for all HyTES bands estimated using a principal components regression.  Data is in a lines x samples x bands matrix.  Bands = 256 covering wavelenghts of 7.4 to 12 µm.
L2_Emissivity_PC_Wavelengths	Wavelengths in µm for each band (n=256) for L2_Emissivity_PC data.
L2_LST	Land surface temperature in Kelvin in lines x samples matrix.  Data in lines x samples x 1 band.
Transmission	Atmospheric transmittance. One value per 256 sensor bands.
pixel_geolocation	Georeferencing information for each pixel in lines x samples x 4 bands: latitude (degrees_north), longitude (degrees_east), height (m), and number of steps taken during ray-casting for each pixel.

A primary goal of the SHIFT campaign was to collect a repeated dense time series of airborne Visible to ShortWave Infrared (VSWIR) airborne imaging spectroscopy data with coincident field measurements. The AVIRIS NG instrument collects VSWIR data that will be combined with in-situ measurements of plant diversity and ecophysiology to produce weekly estimates of ecosystem function over the 1,656-km² study area. 

A multispectral thermal imager is also proposed for the SBG mission (Stavros et al., 2023), and the SHIFT campaign sought to demonstrate the joint use of both VSWIR and thermal infrared (TIR) data. TIR data are used to measure land surface temperature (LST), which informs models of water flux from land surface through processes such as evapotranspiration. LST is sensitive to solar heat gains and local cooling effects due to evaporative cooling.  

The HyTES instrument measures TIR radiances that can be used to derive LST, emissivity and Level 3 products such as latent heat flux and detection of air pollution sources.

Standard calibration procedures for the HyTES instrument were followed. HyTES maintains a set of calibration files for each campaign: https://hytes.jpl.nasa.gov/documents/cal.

To derive the emissivity, an In-Scene Atmospheric Correction (ISAC) approach was used.  No additional quality assessment is provided for these data.

The Hyperspectral Thermal Emission Spectrometer (HyTES) is an airborne imaging spectrometer with 256 spectral channels between 7.5 and 12 micrometers in the thermal infrared part of the electromagnetic spectrum and 512 pixels cross-track. HyTES was developed to support the Hyperspectral Infrared Imager (HyspIRI) mission and has been flown since 2012. (Johnson et al., 2011; Hook et al., 2013). It provides high spatial and high spectral resolution data on surface temperature and emissivity (Hulley et al., 2016b). Its capabilities include identification of air pollution point sources (Hulley et al., 2016a) and geological studies. Additional details about the HyTES instrument are available at https://hytes.jpl.nasa.gov.

HyTES flights were carried out over the region of the SHIFT campaign study area (Figure 2) on 23 March 2022 from 10:14 AM to 2:57 PM Pacific Time, resulting in 91 flight scenes. Raw imagery data were processed to Level-1 brightness temperature (radiance) at sensor (Rivera et al., 2023). Level 2 emissivity and land surface temperature (LST) were derived from these L1 data.

Emissivity Data (L2_Emissivity)

This array contains HyTES emissivity spectral data from 8-11.5 µm with the same dimensions as the L1 data, except only 202 'window bands' were retrieved instead of 256. This is the standard emissivity product derived using the Temperature Emissivity Separation (TES) algorithm (Gillespie et al., 1998) with an In-Scene Atmospheric Correction (ISAC) approach for HyTES channels from 8-11.5 µm using only clear window channels and well-calibrated data. Spectral emissivity from 7.4-8 µm cannot be accurately derived due to strong water vapor absorption features in this spectral domain. TES was not applied to channels above 11.5 µm due to issues with calibration.

PC Regression Emissivity Data (L2_Emissivity_PC)

This array contains HyTES emissivity data from 7.4-12 µm with the same dimensions as the Level 1A data. In order to produce emissivity for all HyTES bands, a separate product was generated.  This product was derived using a Principal Component (PC) eigenvector regression approach to produce emissivity for all 256 HyTES channels. The eigenvectors were calculated using a set of ~150 lab spectra similar to the approach used to generate the MODBF product (Seemann et al., 2008).  This technique produces a smoother spectrum that will fit all the original L2_Emissivity data and extend emissivity estimates below 8 µm and above 11.5 µm.  Caution should be used when using this L2_Emissivity_PC product  to identify geologic features because some features may be smoothed out or absent.

Land Surface Temperature Data 

LST Products were derived from atmospherically corrected L1 radiance data using the TES algorithm. These LST data are in units of Kelvin with the same dimensions as the L1 data except there is only one band.

Figure 2.  Footprints (blue rectangle) of HyTES flight scenes acquired on March 23 2022 for the SHIFT campaign over Santa Barbara County, California, U.S. Basemap: ©OpenStreetMap contributors.

Gillespie, A., S. Rokugawa, T. Matsunaga, J.S. Cothern, S. Hook and A. B. Kahle. 1998. A temperature and emissivity separation algorithm for Advanced Spaceborne Thermal Emission and Reflection Radiometer (ASTER) images. IEEE Transactions on Geoscience and Remote Sensing 36:1113-1126. https://doi.org/10.1109/36.700995

Hook, S.J., W.R. Johnson,  and M.J. Abrams. 2013. NASA’s Hyperspectral Thermal Emission Spectrometer (HyTES). In: C. Kuenzer and S. Dech (eds). Thermal Infrared Remote Sensing. Remote Sensing and Digital Image Processing, vol 17. Springer, Dordrecht. https://doi.org/10.1007/978-94-007-6639-6_5

Hulley, G.C., R.M. Duren, F.M. Hopkins, S.J. Hook, N. Vance, P. Guillevic, W. R. Johnson, B.T. Eng, J.M. Mihaly, V.M. Jovanovic, S.L. Chazanoff, Z.K.Staniszewski, L. Kuai, J. Worden, C. Frankenberg, G. Rivera, A.D. Aubrey, C.E. Miller, N.K. Malakar, J.M. Sánchez Tomás, and K.T. Holmes. 2016a. High spatial resolution imaging of methane and other trace gases with the airborne Hyperspectral Thermal Emission Spectrometer (HyTES). Atmospheric Measurement Techniques 9:2393–2408. https://doi.org/10.5194/amt-9-2393-2016

Hulley, G.C., R.J. Freepartner, and S. J. Hook. 2023. SHIFT: HyTES L3 Geolocated Multispecies Gas Products, March 23 2022. ORNL DAAC, Oak Ridge, Tennessee, USA. https://doi.org/10.3334/ORNLDAAC/2247

Hulley, G.C., S. Hook, W. Johnson, P. Guillevic, and N. Malakar. 2016b. Hyperspectral Thermal Emission Spectrometer (HyTES) Level-2 Land Surface Temperature and Emissivity Algorithm Theoretical Basis Document. NASA Jet Propulsion Laboratory, California Institute of Technology; Pasadena, California.

Johnson, W.R., S. J. Hook, P. Mouroulis, D.W. Wilson, S.D. Gunapala, v. Realmuto, A. Lamborn, C. Paine, J.M. Mumolo, and B.T. Eng. 2011. HyTES: Thermal imaging spectrometer development. IEEE Explore: Conferences, 2011 Aerospace Conference, Big Sky, Montana, USA. https://doi.org/10.1109/AERO.2011.5747394

Rivera, G., W.R. Johnson, R.J. Freepartner, B. Eng, and S.J. Hook. 2023. SHIFT: HyTES L1 Brightness Temperature, March 23 2022. ORNL DAAC, Oak Ridge, Tennessee, USA. https://doi.org/10.3334/ORNLDAAC/2245

Seemann, S.W., E.E. Borbas, R.O. Knuteson, G.R. Stephenson, and H. Huang, 2008.  Development of a global infrared land surface emissivity database for application to clear sky sounding retrievals from multispectral satellite radiance measurements. Journal of Applied Meteorology and Climatology 47:108–123. https://doi.org/10.1175/2007JAMC1590.1

Stavros, E.N., J. Chrone, K. Cawse-Nicholson, A. Freeman, N. F. Glenn, L. Guild, R. Kokaly, C. Lee, J. Luvall, R. Pavlick,  B. Poulter, S.S. Uz, S. Serbin, D.R. Thompson, P.A. Townsend, K. Turpie, K. Yuen, K. Thome, W. Wang, S.-K. Zareh, J. Nastal, D. Bearden, C.E. Miller, and D. Schimel. 2023. Designing an observing system to study the Surface Biology and Geology (SBG) of the Earth in the 2020s. Journal of Geophysical Research: Biogeosciences 128:e2021JG006471. https://doi.org/10.1029/2021JG006471