NASA-ESA Cooperation on the SBG and CHIME Hyperspectral Satellite Missions: a roadmap for the joint Working Group on Cal/Val activities

&amp;lt;p&amp;gt;Imaging spectroscopy has been identified by ESA, NASA and other international space agencies as key to addressing a number of most important scientific and environmental management objectives. To implement the critical EU- and related policies for the management of natural resources, assets and benefits, and to achieve the objectives outlined by NASA&amp;amp;#8217;s Decadal Survey in ecosystem science, hydrology and geology, high fidelity imaging spectroscopy data with global coverage and high spatial resolution are required. As such, ESA&amp;amp;#8217;s CHIME (Copernicus Hyperspectral Imaging Mission for the Environment) and NASA&amp;amp;#8217;s SBG (Surface Biology and Geology) satellite missions aim to provide imaging spectroscopy data at global coverage at regular intervals of time with high spatial resolution.&amp;lt;/p&amp;gt;&amp;lt;p&amp;gt;However, the scientific and applied objectives motivate more spatial coverage and more rapid revisit than any one agency&amp;amp;#8217;s observing system can provide. With the development of SBG and CHIME, the mid-to-late 2020s will see more global coverage spectroscopic observing systems, whereby these challenging needs can be more fully met by a multi-mission and multi-Agency synergetic approach, rather than by any single observing system.&amp;lt;/p&amp;gt;&amp;lt;p&amp;gt;Therefore, an ESA-NASA cooperation on imaging spectroscopy space missions was seen as a priority for collaboration, specifically given the complementarity of mission objectives and measurement targets of the SBG and CHIME. Such cooperation is now being formalized as part of the ESA-NASA Joint Program Planning Group activities.&amp;lt;/p&amp;gt;&amp;lt;p&amp;gt;Among the others, calibration and validation activities (Cal/Val) are fundamental for imaging spectroscopy while the satellites are in-orbit and operating. They determine the quality and integrity of the data provided by the spectrometers and become even more crucial when data from different satellites, carrying different imaging sensors, are used by users worldwide in a complementary and synergetic manner, like it will be the case for CHIME and SBG data. Indeed, Cal/Val activities not only have enormous downstream impacts on the accuracy and reliability of the products, but also facilitate cross-calibration and interoperability among several imaging spectrometers, supporting their synergistic use. Accordingly, within the context of this cooperation, a Working Group (WG) on Calibration/Validation has been set up, aiming to establish a roadmap for future SBG-CHIME coordination activities and collaborative studies.&amp;lt;/p&amp;gt;&amp;lt;p&amp;gt;This contribution aims to outline the key areas of cooperation between SBG and CHIME in terms of Calibration and Validation, and present the establishment of a roadmap between the two missions, focusing on the following topics:&amp;lt;/p&amp;gt;&amp;lt;ul&amp;gt;&amp;lt;li&amp;gt;Establishing an end-to-end cal/val strategy for seamless data products across missions, including transfer standards;&amp;lt;/li&amp;gt; &amp;lt;li&amp;gt;Measurement Networks and commonly recognised Cal/Val reference sites;&amp;lt;/li&amp;gt; &amp;lt;li&amp;gt;Status of atmospheric radiative transfer and atmospheric&amp;amp;#8211;correction procedures;&amp;lt;/li&amp;gt; &amp;lt;li&amp;gt;Standardisation and Quality Control of reference data sets;&amp;lt;/li&amp;gt; &amp;lt;li&amp;gt;Definition and implementation of joint airborne spectroscopy campaigns, such as the executed 2018 and planned 2021 campaigns, to simulate both missions and exercise the capabilities needed for eventual interoperability (incl. data collection, calibration, data product production);&amp;lt;/li&amp;gt; &amp;lt;li&amp;gt;Continuous validation throughout the lifetime of products;&amp;lt;/li&amp;gt; &amp;lt;li&amp;gt;Identifying other opportunities for efficiency and success through cooperation on calibration and validation, downlink capabilities and shared algorithms (e.g. compression and on-board data reduction).&amp;lt;/li&amp;gt; &amp;lt;/ul&amp;gt;