Assessment of the spectral stability of Libya 4, Libya 1, and Mauritania 2 sites using Earth Observing One Hyperion

Abstract

The objective of this paper is to formulate a methodology to assess the spectral stability of the Libya 4, Libya 1, and Mauritania 2 pseudo-invariant calibration sites (PICS) using Earth Observing One (EO-1) Hyperion sensor. All the available Hyperion collections, downloaded from the Earth Explorer website, were utilized for the three PICS. In each site, a reference spectrum is selected at a specific day in the vicinity of the region of interest (ROI) defined by Committee on Earth Observation Satellites (CEOS). A series of ROIs are predefined in the along-track direction with 196 spectral top-of-atmosphere reflectance values in each ROI. Based on the reference ROI spectrum, the spectral stability of these ROIs is evaluated by average deviations (ADs) and spectral angle mapper (SAM) methods in the specific ranges of time and geo-spatial locations. Time and ROI location-dependent SAM and AD results are very stable within AE2 deg and AE1.7% of 1σ standard deviations. Consequently, the Libya 4, Mauritania 2, and Libya 1 CEOS selected PICS are spectrally stable targets within the time and spatial swath ranges of the Hyperion collections.

Monitoring Orbital Precession of EO-1 Hyperion With Three Atmospheric Correction Models in the Libya-4 PICS

“…Our results appear consistent with other studies that found Hyperion TOA radiances to be spectrally stable within 5% in the VNIR and 10% in the SWIR [27]. Figure 2 displays trends, CV, and R 2 (p-val < 0.01) for reflectance in 172 calibrated bands retrieved with AT, AC and F 135 models.…”

“…These results suggest Libya-4 is an ideal location to monitor the impacts of orbital 79 precession on Hyperion data products. Other studies have examined the Hyperion TOA VSWIR 80 temporal trend in the Libya-4 PICS and found it to be stable within 2.5 -5 % in most spectral 81 bands [27]. However, this is the first study, to our knowledge, to examine Hyperion's surface 82 reflectance trends associated with EO-1's rapid orbit degradation years (2014+).…”

Classification of North Africa for Use as an Extended Pseudo Invariant Calibration Sites (EPICS) for Radiometric Calibration and Stability Monitoring of Optical Satellite Sensors

“…However, this landcover classification applies to many current PICS extensively used for sensor radiometric calibration and performance analysis, such as Libya 4, Mauritania 1, and Algeria 1 [5,8,21,22]. Choi et al [41] studied the spectral stability of the Libya 4, Libya 1 and Mauritania 2 PICS using average deviation (AD) and spectral angle mapper (SAM) where average deviation is the absolute reflectance difference and SAM is the spectral angle between the test and reference spectrum [42,43]. This is the earliest attempt to study the spectral similarity of PICS and in this study, they found that ROIs chosen parallel to the along-track direction were spectrally stable for spectral angle mapper values up to ±2 degrees, with an average deviation of ±1.7% in reflectance scale.…”

Analysis of Spatial and Temporal Variability in Libya-4 with Landsat 8 and Sentinel-2 Data for Optimized Ground Target Location

“…It is located in the Great Sand Sea (28.55 • N, 23.39 • E) at an average height of 118 m above sea level. The study area was covered by unvegetated sand dunes and it usually had high atmospheric stability with low aerosol content as well as a low presence of cloudiness [24].…”