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PROBA-V QWG meeting 16

22-Mar - 23-Mar 2023

Hybrid event

The main topics of the meeting were recalled with summary of current status and open points for discussion:

Mission Status and Calibration:  since end of Proba-V Experimental Phase (October 2021) the vegetation instrument was switched to standby mode and limited maintenance calibration segments are acquired with the aim of monitoring the temporal stability of the sensor and the instruments’ health status. The number of planned calibrations is limited by the downlink constraints although few X-band passes per month were added since summer 2022 to acquire over Gobabeb site. Currently following acquisitions are planned for monitoring purposes: a) acquisitions over the two RadCalNet sites (Railroad Valley Playa - USA and Gobabeb - Namibia) to assess the radiometric absolute calibration and the geometric performances as well as the temporal stability; b) Dark Current monitoring to monitor temperature increase in the optical bench mainly due to the instrument ageing and orbital drift effects; c) Lunar acquisitions on a monthly basis to gather valuable data in support of the validation of ESA Lunar Irradiance Model (LIME). During the meeting these calibrations activities will be reviewed also considering the current platform status presented by REDU and its impacts on the acquisitions results.

Collection 2 and Collection 3:  the full Proba-V C2 reprocessing is now completed, and a detailed Validation Report has been provided by VITO to the QWG. The C2 TOC products were certified as CEOS-ARD compliant and endorsed by CEOS-Land Surface Imaging Virtual Constellation and CEOS Working Group on Calibration & Validation. The overall accuracy has largely improved with respect to C1, namely: C2 shows more clear observations than in C1 at all resolutions and the C1 issues related to the dependency of cloud masking on the latitude are solved. The differences between C1 and C2 at TOA level are small whereas larger bias is observed at TOC level in the BLUE and RED bands over densely vegetated areas where the observed C2 NDVI is lower. Finally high correspondence between SPOT-VGT and Proba-V is observed for both collections as well as a strong correspondence of C2 NDVI with MetOp/AVHRR (EUMETSAT Satellite Application Facility on Land Surface Analysis/LSA-SAF) ENDVI10 and MODIS MOD13A3 NDVI time series. First feedback on C2 will be provided by UCL as first user of the collection and analyzed within the QWG. During the meeting the endorsement of the release of C2 data to the users will be discussed as well as the preparation of the future C3 baseline. The C3 reprocessing activity will be conducted as part of the FDR4VGT project with the main objective to ensure a consistent and harmonized LTDR of TOA L1C products from VGT1/VGT2/PV 20+ years archive.

Continuity: several progresses were made during 2022 to enhance the consistency of Proba-V and S3 SYN-VGT, although some quality issues and large discrepancies in the historical mission data for the 2020-2022 period remain and require a full reprocessing of the archive to obtain a consistency in the VGT-PV-S3 LTDR. The CGLS biophysical products processing chain switched to S3 and the analysis on S3-Proba-V derived products shown a good quality and overall temporal and spatial consistency.

Proba-V Companion Cubesat: the PV-CC launch was delayed due to Vega-C failure, the current launch schedule is set for end of summer 2023 and the commission phase is planned to last three months. The first objective of this IOD is to verify that the in-orbit performances of such small Cubesat are comparable to those of bigger platforms, this IOD will be key to set the ground of future potential constellation for increasing the revisit time. The PV-CC Cal/Val plan is well consolidated and widely discussed within the QWG, the focus will be on the reuse of Proba-V know-how and its infrastructure and on RadCalNet and S2-cross-over as benchmark for radiometry and geometry. During the meeting the proposal on a synergistic exploitation in combination with Sentinel-2 will be discussed and the PV-CC revisit time and global coverage analysed for data exploitation purposes.

A summary of the Minutes of Meeting is available here.