Artist impression of EO-1 satellite, that carried the Hyperion hyperspectral instrument. Image courtesy of NASA.
Hyperspectral data looks like it will be the next big development in remote sensing with contracts issued last week by the United States National Reconnaissance Office (NRO).
Hyperspectral imaging is where the electromagnetic spectrum is broken down into many, often hundreds of, narrow spectral bands which are collected together. This contrasts with multispectral missions, such as Sentinel-2 or Landsat, which collect only a small number of bands. Hyperspectral bands tend to be narrower to create the increased number, meaning that, for example, within agriculture, individual crops can be identified, rather than simply vegetation. Other applications include geology, forestry, environmental monitoring and security.
In the early 1980s the first hyperspectral instrument, the Airborne Imaging Spectrometer, was developed by the Jet Propulsion Laboratory (JPL) as an experimental testbed. Further work by NASA and JPL turned this into the Airborne Visible/Infrared Imaging Spectrometer (AVIRIS), the first instrument to fully support hyperspectral imaging for Earth remote sensing. It was launched in 1993 and collected data for 224 spectral bands, ranging from 380 to 2510 nanometres. It was an airborne based solution and was flown on a number of aircraft.
The first satellites with hyperspectral images on board were NASA’s Earth Observer-1 (NMP/EO-1), with the spectrometer Hyperion which had 242 spectral bands and was launched in November 2000, and the European Space Agency’s PRoject for OnBoard Authonomy (PROBA) satellite carrying the Compact High Resolution Imaging Spectrometer (CHRIS) which was launched in October 2001 and was a hyperspectral instrument, but downloaded a maximum of 19 spectral bands.
US National Reconnaissance Office Contracts
Hyperspectral data is in the news this week following the six study contracts awarded by the NRO for commercial hyperspectral imagery. The contracts aim to understand the current, and expected, hyperspectral imagery availability, quality, and operational capacity, together with what it might add their existing capabilities. The contracts will focus on both analytical studies to provide estimates of system capabilities for individual sensors and constellations, together with assessments of in-orbit capabilities and procuring data products. The six contracts were awarded to:
- BlackSky Technology
- HyperSat
- Orbital Sidekick
- Pixxel
- Planet
- Xplore
What’s really interesting about this contract is that Pixxel, an Indian company, is the only one with an existing hyperspectral imaging satellite in space. It also plans to launch a further six satellites later this year. The other five American companies have all either got plans already for, or are expressing interest in, moving into the hyperspectral space.
- HyperSat is planning a constellation of six HyperSat satellits offer hyperspectral capabilities across 50 spectral bands, with the first satellite expected to launch early this year. However, this is currently scheduled to be launched by Virgin Orbit’s LauncherOne which failed in Cornwall last year, and with the company currently pausing operations to seek financing this could impact plans.
- Orbital Sidekick, is also planning a six satellite constellation for its GHOSt (Global Hyperspectral Observation Satellite) hyperspectral satellite which will offer 400 spectral bands with the first satellite due to be launched later this year.
- Xplore aims to launch their first Xcraft hyperspectral satellite in the latter part of 2023, which will offer hyperspectral data with 2m and 5m spatial resolution. Xplore plan to establish a constellation of 12 satellites.
- Planet is also planning to launch hyperspectral satellites later this year. The satellites will be known as Tanager, and the first two are expected to be launched in 2023 with a larger constellation following in 2025.
- BlackSky does not currently have any hyperspectral capabilities, but in a press release following the contract award it noted that as the company had optical, SAR, radio data and analytics skills, hyperspectral capabilities were a natural extension for their business. No details yet on how they will achieve it, whether that will be launching their own satellites or signing contracts for access to others hyperspectral data – similar to how Maxar recently signed a contract with Umbra for dedicated access to their SAR data.
Hyperspectral Challenges
Hyperspectral data is something Pixalytics knows reasonably well having completed a variety of contracts and work involving this type of data. Whilst it is obviously remote sensing data, the increased number of spectral bands means the data files are larger and it is more difficult to calibrate and to extract the information you are really interested in, due to the sheer amount of data. Similarly, some existing remote sensing tools are not as effective with hyperspectral data; although, this has been improving as more hyperspectral satellites as EnMAP and PRISMA have been launched.
It is an interesting development in the field, and as the new satellites are launched the amount of hyperspectral data available looks set to explode.
