Using scattered light from nadir port to aid the Terra and Aqua MODIS reflective solar band calibration

Amit Angal; Xiaoxiong Xiong; Kevin Twedt; Junqiang Sun

doi:10.1117/12.2676999

4 October 2023 Using scattered light from nadir port to aid the Terra and Aqua MODIS reflective solar band calibration

Amit Angal, Xiaoxiong Xiong, Kevin Twedt, Junqiang Sun

Proceedings Volume 12685, Earth Observing Systems XXVIII; 126851D (2023) https://doi.org/10.1117/12.2676999
Event: SPIE Optical Engineering + Applications, 2023, San Diego, California, United States

Abstract

The MODIS instruments on the Terra and Aqua spacecraft employ a solar diffuser (SD) and a solar diffuser stability monitor (SDSM) system to calibrate their reflective solar bands (RSBs), covering a spectral range from 0.4 to 2.1 μm. The UV exposure of the SD, from its sun-view port as well as the scattered light (sunlight reflected from top-of-atmosphere), has led to a wavelength dependent degradation of the SD, with larger degradation observed at shorter wavelengths. The scatter off the diffuser onto the scan mirror is in the forward direction, whereas the scatter off the diffuser onto the SDSM fold mirror is in the backward direction. Since the outgoing angles (viewed by MODIS detectors) are the same as the scheduled SD calibration, the gain derived from scattering light facilitates monitoring the dependence of the SD’s degradation on incident angles. In this paper, we present a method that uses multiple orbits over each mission to obtain a SD response to the nadir port illumination. The SD degradation estimated from the nadir port illumination is compared with the degradation derived from the sun-illuminated SD. As both Terra and Aqua spacecraft continue to drift from their nominal orbits, the SD calibration mechanism has been adapted to these drifts, especially in terms of characterizing the transmission screen function. This paper also presents the utility of this scattering light data to support the RSB calibration in the post-nominal orbit drift era of operations.

(2023) Published by SPIE. Downloading of the abstract is permitted for personal use only.

Citation Download Citation

Amit Angal, Xiaoxiong Xiong, Kevin Twedt, and Junqiang Sun "Using scattered light from nadir port to aid the Terra and Aqua MODIS reflective solar band calibration", Proc. SPIE 12685, Earth Observing Systems XXVIII, 126851D (4 October 2023); https://doi.org/10.1117/12.2676999

ACCESS THE FULL ARTICLE

INSTITUTIONAL
Select your institution to access the SPIE Digital Library.

SELECT YOUR INSTITUTION

PERSONAL
Sign in with your SPIE account to access your personal subscriptions or to use specific features such as save to my library, sign up for alerts, save searches, etc.

PERSONAL SIGN IN

No SPIE Account? Create one

PURCHASE THIS CONTENT

SUBSCRIBE TO DIGITAL LIBRARY

50 downloads per 1-year subscription

Members: $195

Non-members: $335 ADD TO CART

25 downloads per 1 - year subscription

Members: $145

Non-members: $250 ADD TO CART

PURCHASE SINGLE ARTICLE

Includes PDF, HTML & Video, when available

Members: $17.00

Non-members: $21.00 ADD TO CART

PROCEEDINGS
8 PAGES

DOWNLOAD PAPER SAVE TO MY LIBRARY

GET CITATION

RIGHTS & PERMISSIONS

Get copyright permission Get copyright permission on Copyright Marketplace

KEYWORDS

MODIS

Calibration

Light scattering

Equipment

Mirrors

Scattered light

Reflectivity

Show All Keywords

Keywords/Phrases

Search In:

Publication Years