SPOT-4 (Take 5): Simulation of Sentinel-2 Time Series on 45 Large Sites

Abstract

This paper presents the SPOT-4 (Take 5) experiment, aimed at providing time series of optical images simulating the repetitivity, the resolution and the large swath of Sentinel-2 images. The aim was to help users set up and test their applications and methods, before Sentinel-2 mission data become available. In 2016, when both Sentinel-2 satellites are operational, and for at least fifteen years, users will have access to high resolution time series of images systematically acquired every five days, over the whole Earth land surfaces. Thanks to Sentinel-2's high revisit frequency, a given surface should be observed without clouds at least once a month, except in the most cloudy periods and regions. In 2013, the Centre National d'Etudes Spatiales (CNES) lowered the orbit altitude of SPOT-4, to place it on a five-day repeat cycle orbit for a duration of five months. This experiment started on Remote Sens. 2015, 7 12243 31 January 2013 and lasted until 19 June 2013. SPOT-4 images were acquired every fifth day, over 45 sites scattered in nearly all continents and covering very diverse biomes for various applications. Two ortho-rectified products were delivered for each acquired image that was not fully cloudy, expressed either as top of atmosphere reflectance (Level 1C) or as surface reflectance (Level 2A). An extensive validation campaign was held to check the performances of these products with regard to the multi-temporal registration, the quality of cloud masks, the accuracy of aerosol optical thickness estimates and the quality of surface reflectances. Despite high a priori geo-location errors, it was possible to register the images with an accuracy better than 0.5 pixels in the large majority of cases. Despite the lack of a blue band on the SPOT-4 satellite, the cloud and shadow detection yielded good results, while the aerosol optical thickness was measured with a root mean square error better than 0.06. The surface reflectances after atmospheric correction were compared with in situ data and other satellite data showing little bias and the standard deviation of surface reflectance errors in the range (0.01-0.02). The Take 5 experiment is being repeated in 2015 with the SPOT-5 satellite with an enhanced resolution.

Early Detection of Summer Crops Using High Spatial Resolution Optical Image Time Series

“…It was finally deorbited, when the Take5 program [38] took place (from February to June 2013) to prepare further analyses of time series acquired by ESA's Sentinel-2 mission. Spot 5 was launched in May 2002.…”

Satellite remote sensing reveals a positive impact of living oyster reefs on microalgal biofilm development

“…Landsat 5 and 8 data were downloaded from the US Geological Survey (USGS) Earth Explorer data portal (http://earthexplorer.usgs.gov/). Most SPOT data were acquired on demand by the CNES (Centre National d'Etudes Spatiales) and Airbus Defence & Space, with the exception of the Take 5 data (Hagolle et al, 2015b) which were freely available from the Theia Land Data Centre web portal (https://www.theia-land.fr/en). The Theia data portal was also used to download some Landsat 5 data.…”

Assessment of an Operational System for Crop Type Map Production Using High Temporal and Spatial Resolution Satellite Optical Imagery

“…For this, simulations of Sentinel-2 time series based on SPOT4 (Take5) [13] and Landsat 8 data [14] were used.…”

“…The SPOT4 (Take5) and Landsat 8 data were processed to Level 2A (i.e., surface reflectance values with masks for clouds, cloud shadows, snow and water), as described in [13], using the Multi-Sensor Atmospheric Correction and Cloud Screening (MACCS) processor, developed and maintained at the Centre d'Etudes Spatiales de la BIOsphère (CESBIO; [34]). …”