## 2 Scope: Specifying a Satellite for Archaeology  
In considering the question of what a satellite for archaeology might look like, a scope has been defined for a specific form of archaeological prospection. This is used as a device to help consider the relationships between archaeological imperatives and satellite system design, recognising that, even with a theoretical question, an element of feasibility is required and that a 'do everything'approach would over-complicate the issues. As such, sensors, platforms, and data processing and interpretation workflows remain out of scope for the paper, without wishing to underplay their importance. Instead, by focusing on the orbital mechanics of the system, this work presents a mission architecture that could meet the spatial and temporal resolution requirements for archaeological prospection with existing imaging technology. At a high level, the scope is defined with the need to cover the whole of Scotland (c. 80,000 km\({}^{2}\)), with regular revisit periods and GSD of \(<\)1 m in multi-spectral data. Such data could be expected to inform a range of activities, including archaeological prospection, condition monitoring, and landscape-scale change detection. The required GSD is specified at \(<\)1 m to enable clear identification of archaeological features at a scale of 1 m and smaller, where a higher GSD would result in insufficient spatial resolving power to do so (Figure 1). A core objective is to contribute to the creation of systematic national data [13; 14], and because of this aspiration to deal with very large areas, solutions like UAVs or localised survey methods do not provide the necessary data coverage. Within this general framework, a specific aspect of scope focusses on those otherwise buried archaeological remains that are expressed through crop proxies. The emergence of cropmarking is dependent on climatic conditions, soil properties and land-use patterns which introduce considerable variation in the timing and potential for formation [15]. These factors necessitate regular revisit periods, as crop development across even relatively small areas is not uniform through the summer and is thus time critical. Crop proxies are used for archaeological prospection across the European continent and Scotland is selected as a study region with the understanding that the presented method of space system architecture design could be applied to other regions. It should be noted, however, that the latitude, prevailing weather and timing of the crop season in the region of interest will impact the solution obtained. Figure 1: Many archaeological sites in Scotland, and indeed elsewhere in Europe, are composed of relatively small discrete features, as this example of an early medieval cometary at Croftgowan in Highland illustrates. The discrete features that make up the site are characterised by ditches often \(<\)1 m across and small burial pits. The scale of expected features requires a GSD of \(<\)1 m to enable clear identification of archaeological features. Graphic: [PERSON]; Source image DP281499 \(\copyright\) Historic Environment Scotland. In Scotland, the distributions of soils that are conducive to crommark formation and appropriate land use (mainly arable crops, but in extreme droughts also pasture) are largely in the east and south of the country (Figure 2), so this represents a specific area of interest. Archaeological prospection in these areas is currently dependent on a light aircraft-based observer-directed survey, informed by broad-brush soil moisture deficit data as a proxy for areas of likely crop stress. On this basis, prospection is undertaken relying on visual identification of crommarking and selective imaging, in an approach that is recognised as introducing significant bias in what is observed and recorded [16; 17; 18; 19]. This 'crommark survey' then is a central focus for the specification of our satellite for archaeology, alongside monitoring of designated archaeological sites for which multi-temporal high-resolution imaging is required.