AVIRIS-NG (Airborne Visible/Infrared Imaging Spectrometer-Next Generation) / NGIS
In 2007, the JPL team began to conceptualize the next generation of an airborne AVIRIS-like sensor (referred to as AVIRISng) based on input from the research community and potential partners. Internally funded efforts at JPL created progress in the system concepts for such a new sensor. The instrument team finalized the requirements and and design work and completed a design review in November 2009. The NGIS (Next Generation Imaging Spectrometer) design is one outcome of that work. The instrument has been built and integrated, the target completion date is mid-summer 2011. 1) 2)
The NGIS instrument is compatible with a broad array of possible aircraft platforms. Initial flights will take place in a Twin Otter turboprop at altitudes of ~10-15 km.
Major components of the flight package (Figure 1) include the sensor itself, which will be encased in a vacuum enclosure, high precision INS/GPS, focal plane electronics, On-Board Calibrator (OBC) electronics boxes, heaters boxes, and a vibration isolating aircraft mount. Accommodation has been made for companion instruments which may be flown in a co-boresighted configuration at the discretion of the project scientist, but are not part of this development. Companion instruments of value may include an optical camera or LIDAR.
Figure 1: Major components of the NGIS flight package and optional companion instruments (image credit: NASA/JPL)
The instrument itself is ~85 cm tall and 53 cm in diameter. Major components include the optical telescope and spectrometer benches, the detector, the source for the OBC (On Board Calibrator) and kinematic struts which suspend the assembly from the instrument backplate. The sensor is housed with a vacuum container and three thermal shields and operated at temperatures of down to -40ºC at the detector. The maintenance of stable temperature across the instrument is vital to minimizing thermal distortions which could affect the optical alignment. The operational temperature is maintained by the operation of two cyrocoolers. This change to active cooling from the passive cryogen approach used for AVIRIS allows operation for up to 14 days at a time with only minimal maintenance of the vacuum.
AVIRIS-NG features new slit and grating technologies as well as new two-mirror all-reflective telescope.
Figure 2: Optical layout of AVIRIS-NG (image credit: NASA/JPL)
Figure 3: Illustration (CAD model) of the NGIS instrument (image credit: NASA/JPL)
Table 1: Key performance characteristics of the NGIS instrument
Figure 4: Photo of the AVIRIS-NG assembly (image credit: NASA/JPL)
• AVIRIS-NG became operational in early 2013. It has been flying on both a Twin Otter aircraft and aboard the NASA ER-2 aircraft. It is available for use by NASA-approved scientists who wish to conduct ecological or mineralogical studies. One of the first flight campaigns of the 2013 season will be over-flying the site of the 2010 Deep Horizons Oil Spill off Texas and Louisiana in the United States. 3)
• First flight: In April 2012, AVIRIS-NG — a new instrument developed to support NASA’s Terrestrial Ecology Program and the planned HyspIRI mission — successfully completed its first flight onboard NASA’s Twin Otter aircraft. 4) 5)
The first flight of AVIRIS-NG successfully demonstrated a thermal, actively cooled design that limits opto-thermal-mechanical distortions to less than 0.01% of a pixel. Another achievement of note, AVIRIS-NG demonstrated a new alignment methodology for optical instruments including the alignment of a HgCdTe focal plane at an ambient temperature (273 K).
Figure 5: AVIRIS-NG first spectra from the first flight on April 22, 2012 (image credit: NASA/JPL) 6)
1) L. Hamlin, R. O. Green, P. Mouroulis, M. Eastwood, D. Wilson, M. Dudik, C. Paine, “Imaging Spectrometer Science Measurements for Terrestrial Ecology: AVIRIS and New Developments,” ESTF 2011 (Earth Science Technology Forum 2011), Pasadena, CA, USA, June 21-23, 2011, URL: http://esto.nasa.gov/conferences/estf2011/papers/Hamlin_ESTF2011.pdf
2) “Next Generation Airborne Visible/Infrared Imaging Spectrometer (AVIRISng),” NASA/JPL, URL: http://airbornescience.jpl.nasa.gov/instruments/avirisng/
3) Information provided by Louise Hamlin, Manager, JPL Next Generation Imaging Spectrometers (NextGen IS)
4) Jack A. Kaye, “Challenges And Successes In Creating Multi-instrument/Multi-platform Space-Based Earth System Data Records,” July 31, 2012, URL: http://www1.ncdc.noaa.gov/pub/data/sds/cdr/presentations/other/kaye-2012.pdf
6) “AVIRIS Next Generation First Spectra, “ URL: http://aviris.jpl.nasa.gov/documents/pres_AVIRIS_NG_for_web_120430a_srl.pdf
The information compiled and edited in this article was provided by Herbert J. Kramer from his documentation of: ”Observation of the Earth and Its Environment: Survey of Missions and Sensors” (Springer Verlag) as well as many other sources after the publication of the 4th edition in 2002. - Comments and corrections to this article are always welcome for further updates.