ProSpecTIR Mineral Exploration

Mineral exploration in the western United States using visible – short wave infrared
and a mid wave – long wave infrared hyperspectral imagers: Joint Airborne
Collection using Hyperspectral Systems (JACHS)
Abstract:
In June, 2008 a joint airborne of collection using hyperspectral systems was tested on a single Twin
Otter aircraft. This experiment was designed to incorporate two airborne hyperspectral sensors for
geological and environmental projects. Mineral exploration and environmental impact statements are
two areas where full spectrum hyperspectral data can document the mineralogy at the surface prior to
mining operations. Many previous hyperspectral remote sensing collections were collected on a single
aircraft with a single sensor. Mineral mapping using hyperspectral sensors that measure in
complimentary regions of the electromagnetic spectrum is cost effective, as it allows for the mapping of
clays, sulfates, carbonates, feldspars, quartz, garnets, and many other minerals. This report describes the
experiment using the following two hyperspectral sensors: ProspecTIR a VNIR – SWIR sensor with 356
channels and spectral range of 0.4 – 2.5 µm, along with SEBASS, a MWIR – LWIR sensor with 128
channels from 2.5 – 5.3 µm and 128 channels from 7.6 – 13.5 µm. SpecTIR’s ProspecTIR system and
The Aerospace Corporation’s Spatially Enhanced Broadband Array Spectrograph System (SEBASS) are
pushbroom sensors, have high signal to noise ratios, have similar swath widths and instantaneous fields
of view. Examples of data collection experiment will be shown with a focus on mineral/lithologic
identification and mapping along with environmental assessment in the western United States.
Introduction:
Mineral mapping with imaging spectrometers commonly occurs with one sensor on board a single
aircraft. The ProspecTIR sensor from SpecTIR, LLC and the Spatially Enhanced Broadband Array
Spectrograph System (SEBASS) are two such imaging spectrometers. SpecTIR, LLC and The
Aerospace Corporation reached out to several customers to determine the interest in locating these
sensors on the same aircraft, in this case a Twin Otter from Twin Otter International.
Conrad Wright1,V.P. International Development, 9390 Gateway Dr. #100, Reno, Nevada 89521; Conrad@spectir.com
Dean N. Riley2 ,Geologist, 15049 Conference Center Dr. CH1/510, #600, Chantilly, VA 20151; dean.n.riley@aero.org
William A. Peppin1,Geologist, 9390 Gateway Dr. #100, Reno, Nevada 89521;
peppin@spectir.com
Nielson W. Schulenburg2 , Geologist, 15049 Conference Center Dr. CH1/510 #600, Chantilly, VA 20151;
nielson.w.schulenburg@aero.org
1) SpecTIR Corporation, Reno, NV, USA 89521
2) The Aerospace Corporation, Chantilly, VA USA 20151
In June 2008, customer sites, sites releasable to the community, and internal research and development
sites were flown. These sites were in Colorado, New Mexico, Arizona, California, Nevada, and Utah.
Figure 1 shows the approximate location IR&D sites and sites that are releasable to the community
along with the basing locations for the aircraft.
Instrument Information:
The ProspecTIR sensor is an imaging spectrometer that collects 356 spectral images with a 1 to 5 meter
spatial resolution and a 5 nanometer spectral resolution. This sensor measures in the visible to shortwave
infrared (0.4 – 2.5 microns) part of the electromagnetic spectrum and has instantaneous field of view of
1.31 milliradians. SEBASS is an imaging spectrometer that collects 256 spectral images with a spatial
resolution of 1 to 5 meters. The instantaneous field of view is 1.1 milliradians and measures in the
middle infrared (2.5 – 5.3 microns) and the long wave infrared (7.7 – 13.5 microns) of the
electromagnetic spectrum. Both sensors are pushbroom sensors and operate similarly in the aircraft.
Originally, it was conceived that the ProspecTIR sensor would be flown over the camera port in the nose
cone of the Twin Otter and SEBASS in the back on the roll compensation mount over the aft camera
port. However, upon engineering and integration of the sensors, it was determined that the roll
compensation mount could be modified to hold both sensors with about 30 cm of offset between lenses.
The mount was modified and both sensors were integrated on to the mount and the roll compensation
was tested prior to installation on the aircraft. One week later, the sensors and mount were installed on
the aircraft over the aft camera port.
Results:
Data was collected over ten locations with as few as four flight lines to 34 flight lines over two days.
Most of the data were collected at 3 – 5 meter spatial resolution with a few locations at 1 – 1.2 meter
spatial resolution. Here are some preliminary quick looks of the data collected over Cuprite, Nevada.
Figure 2 is a true color mosaic of the 20 flight lines from the ProspecTIR sensor with a 4 meter spatial
resolution. Whereas, figure 3 is a false color composite mosaic of the same 20 flight lines from the
SEBASS sensor with a 3.35 meter spatial resolution.
Conclusion:
This extended abstract highlights the organization, data collection, and cooperative nature that allowed
this unique experiment to occur. Data were successfully delivered to customers. This integration of these
two different, but complementary hyperspectral sensors reduced costs by using one aircraft for
collection. Also, atmospheric and aircraft effects were minimized by locating these sensors on a roll
compensation mount looking through the same camera port in the aft portion of the aircraft. This effort
shows that visible – shortwave infrared wavelength and middle – long wave infrared hyperspectral
sensors can be on the same aircraft with minimal design. From the results and interest of this
experiment, SpecTIR, LLC and the Aerospace Corporation plan to organize and conduct similar
missions in the United States and Australia during 2009.
Figure 1 – Locations of IR&D and sites releasable to the community.
True Color Composite from the ProspecTIR radiance data over Cuprite
(RGB: 0.638 µm, 0.534 µm, 0.460 µm).
Figure 2 – False Color Composite of SEBASS Radiance data over Cuprite
(RGB: 11.33 µm, 12.95 µm, and 9.22 µm)