Ocean Color Instrument
PACE's primary sensor, the Ocean Color Instrument (OCI), is a highly advanced optical spectrometer that will be used to measure
properties of light over portions of the electromagnetic spectrum. It will enable continuous measurement of light at finer wavelength
resolution than previous NASA satellite sensors, extending key system ocean color data records for climate studies.
The color of the ocean is determined by the interaction of sunlight with substances or particles present in seawater such as chlorophyll, a green pigment found in most phytoplankton species. By monitoring global phytoplankton distribution and abundance with unprecedented detail, the OCI will help us to better understand the complex systems that drive ocean ecology.
The OCI is being built at Goddard Space Flight Center (GSFC). It will consist of a cross-track rotating telescope, thermal radiators, along with half-angle mirror and solar calibration mechanisms. The OCI's tilt will help avoid sun glint and single science detector design will inhibit image striping. Its signal-to-noise ratios will rival or exceed previous ocean color instruments. View images of OCI construction here.
The OCI will feature:
View OCI Webinar »
The Coastal Ocean from a Hyperspectral Perspective »
Colors PACE Will See »
Satellite Remote Sensing: Ocean Color (Werdell & McClain, 2019) »
OCI Construction Slideshow »
The OCI's operational concept, cross-track rotating telescope / half-angle mirror, system timing, and data processing infrastructure have been successfully used on previous and existing flight missions such as the Coastal Zone Color Scanner or CZCS (1978 to 1986), Sea-Viewing Wide Field-of-View Sensor or SeaWiFS (1997 to 2010), Suomi National Polar-orbiting Partnership (Visible Infrared Imaging Radiometer Suite or VIIRS), Aqua and Terra (Moderate Resolution Imaging Spectroradiometer or MODIS instrument). In addition, the OCI's avionics (communications, positioning) will use a significantly smaller electronics system developed by the iMUSTANG effort.
The color of the ocean is determined by the interaction of sunlight with substances or particles present in seawater such as chlorophyll, a green pigment found in most phytoplankton species. By monitoring global phytoplankton distribution and abundance with unprecedented detail, the OCI will help us to better understand the complex systems that drive ocean ecology.
The OCI is being built at Goddard Space Flight Center (GSFC). It will consist of a cross-track rotating telescope, thermal radiators, along with half-angle mirror and solar calibration mechanisms. The OCI's tilt will help avoid sun glint and single science detector design will inhibit image striping. Its signal-to-noise ratios will rival or exceed previous ocean color instruments. View images of OCI construction here.
The OCI will feature:
- Cross track, 360° continuous rotating telescope
- Two slit grating hyperspectral spectrographs (ultraviolet to visible & visible to near-infrared, NIR)
- Fiber-coupled multiband filter spectrograph (NIR-to shortwave-infrared)
View OCI Webinar »
The Coastal Ocean from a Hyperspectral Perspective »
Colors PACE Will See »
Satellite Remote Sensing: Ocean Color (Werdell & McClain, 2019) »
OCI Construction Slideshow »
OCI Heritage
The OCI design is based on a long heritage of NASA technology development and flight programs. Its functionality – rotating telescope (mechanism and timing), charged couple device (CCD) detector, optics – benefits from previous technology development efforts such as Ocean Radiometer for Carbon Assessment (ORCA).The OCI's operational concept, cross-track rotating telescope / half-angle mirror, system timing, and data processing infrastructure have been successfully used on previous and existing flight missions such as the Coastal Zone Color Scanner or CZCS (1978 to 1986), Sea-Viewing Wide Field-of-View Sensor or SeaWiFS (1997 to 2010), Suomi National Polar-orbiting Partnership (Visible Infrared Imaging Radiometer Suite or VIIRS), Aqua and Terra (Moderate Resolution Imaging Spectroradiometer or MODIS instrument). In addition, the OCI's avionics (communications, positioning) will use a significantly smaller electronics system developed by the iMUSTANG effort.
OCI Overview
272 kg (600 lb), current best estimate.
237 W, current best estimate.
229.3 cm x 131.1 cm x 130.6 cm (90.3 in x 51.6 in x 51.4 in)
−56.0° to +56.5°, swath width of ~2700 km.
2-day global coverage at 1.2 km (0.75 mi) resolution.
19.9°, aft in the southern hemisphere, fore in the northern hemisphere.
Hyperspectral radiometry from the ultraviolet (340 nm) to near-infrared (895 nm). Bandwidth at 5 nm resolution and spectral steps of 2.5 nm (with spectral steps of 1.25 nm in a limited number of wavelength ranges). Radiances from 315 nm to 340 nm will also be provided, but the radiometric accuracy for those bands is degraded significantly.
Shortwave (SW) infrared (IR) bands include: 940, 1038, 1250, 1378, 1615, 2130, and 2260 nm.
Total calibration of instrument artifacts <0.5% for most bands at top-of-atmosphere. Daily and monthly solar calibrations using two onboard solar diffusers. Bi-monthly lunar calibrations. Monthly linearity measurements with a dim solar diffuser. Verification of hysteresis effects for SWIR bands using signal pulse. Spectral calibration verification using Fraunhofer lines and atmospheric absorption lines.