PRISMA is the hyperspectral mission from the Italian Space Agency (ASI) launched in 2019. It samples the solar irradiance reflected and diffused by the earth-atmosphere system between 400 nm and 2500 nm with a spectral distance better than 11nm and a 30m Ground Sampling Distance. To answer the demanding need of hyperspectral applications, a high absolute radiometric accuracy is required and reached through the combination of on board and natural targets based calibration.
This paper describes PRISMA mission and focuses on the natural targets based calibration methods used to assess the instrument sensitivity. Two methods are used:
- PICS (Pseudo Invariant Calibration Sites) allow to cross-calibrate PRISMA with SENTINEL-2 and 3 ESA missions.
- Gobabeb and La Crau Instrumented sites known as RadCalNet sites which provide a BOA spectral BRDF through a dedicated acquisition protocol and processing as well as atmospheric parameters simultaneously to the satellite pass.
The adaptation of these methods to hyperspectral sensors calibration is presented. The calibrations results which show the very good temporal stability of PRISMA instrument are discussed as well as the methods and in situ instrumentation evolutions planned to improve the calibration of hyperspectral sensors using natural targets.
For Venµs satellite, launched August 2 nd, 2017, the calibration and performance assessment activities of the commissioning phase took place in the second semester of 2017. In particular, the radiometric calibration includes fine tuning of the dynamic, identification of defective pixels, equalization of the detectors, absolute calibration, viewing parameters tuning. A special focus is made on specificities of the mission concerning level-1 radiometric calibration. As far as equalization is concerned: an unusual behavior has been observed on numerous pixels, called “radiometric spikes”, on Venµs images. An improvement of the Venµs radiometric model has been implemented to remove these spikes. Absolute calibration using the moon consists in comparing the global irradiance of the Venµs moon image with the reference from ROLO radiometric model. Absolute calibration using simultaneous nadir observations with Sentinel-2 is also a specificity of the mission: since Sentinel-2A and Sentinel-2B are currently in orbit with very similar spectral bands, it is possible to use Simultaneous Nadir Observations of Venµs and Sentinel-2. The cross-calibration results will be presented and compared to other vicarious calibration methods. About stray-light modelling and correction: the optical stray-light level exceeds the requirements by far. Two types of stray-light are observed: local ghost and cross-talk ghost. Local stray-light model is computed as a global system MTF, whereas the estimated cross-talk contribution is subtracted from the image. The specific correction model and the in-flight results will be presented.
Launched on March 6th, 2017 from Kourou, Sentinel 2B has passed the phase of commissioning. Sentinel 2B will work together with Sentinel 2A launched in June 2015. The building and implementation of the satellite has been made under the responsibility of ESA, for the European Commission. The subset of Image Quality commissioning was delegated by ESA to CNES, referring to the experience of the French Space Agency on previous imagers. This phase lasted 4 months after the launch, a little longer than the formal In Orbit Calibration period conducted by ESA, some Image Quality parameters requiring several months before converging to a stable state. This paper presents the status of the satellite, from an IQ prospective, just before it entered its operational phase. The radiometric and geometric performances are listed, including: the absolute radiometric calibration, the equalization, the SNR, the absolute and the multi-temporal location accuracy. The performances of both satellites Sentinel and Sentinel 2B working together, will be addressed. A particular focus will be done on multi-temporal location performances, homogeneity of radiometric inter calibrations. The accomplishment of the Global Reference Image over Europe is evoked as well. The IQ commissioning phase ended on June 2017. From this date, the monitoring of IQ parameters is under the responsibility of ESA/ESRIN. Nevertheless, CNES continues to support ESA to survey the accuracy of S2A and S2B performances. The article ends by dealing with the prospective offered by the couple Sentinel 2A + Sentinel 2B.
Access to the requested content is limited to institutions that have purchased or subscribe to SPIE eBooks.
You are receiving this notice because your organization may not have SPIE eBooks access.*
*Shibboleth/Open Athens users─please
sign in
to access your institution's subscriptions.
To obtain this item, you may purchase the complete book in print or electronic format on
SPIE.org.
INSTITUTIONAL Select your institution to access the SPIE Digital Library.
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.