## 1 Introduction  
Significant challenges exist in the application of remote sensing data for archaeological prospection and monitoring at a landscape scale. There is a heavy reliance on re-purposed datasets such as aerial photographs, satellite imagery and airborne laser scanning collected for reasons such as cartography, military intelligence and infrastructure planning. This repurposing of data for archaeological purposes is unsurprising as it is expensive to acquire. However, it also brings limitations because the data acquisition was not specified with archaeological imperatives in mind. This paper is a contribution to the discussion of how heritage applications of satellite data might be developed, seeking to reframe the common question of an archaeologist repurposing remote sensing data who might ask 'how can data collected for other purposes be best used to address archaeological questions?'. Rather, the approach taken here is to ask 'what might a satellite system for archaeology look like? ', specifically for a constellation of optical satellites. This exercise has been attempted to explore what an ideal scenario might be--a simulation analysis that foregrounds archaeological survey questions and specifies a satellite system design on that basis. The analysis is framed within imperatives drawn from a specification for imagery in Scotland, which nevertheless illustrates factors that require consideration in specifying such a system anywhere. Specifying 'a satellite for archaeology' is of course a complex multi-faceted process, but the focus here is primarily on mission architecture, considering the number of spacecraft and appropriate orbit selection to deliver the desired spatial resolution and revisit times. While recognising that platforms, sensors, and workflows, to name but a few, are all fundamental aspects of a specification, these are out of the scope of this paper. By exploring mission architecture as one aspect of the design of satellite systems, this paper aims to provide an understanding of the impacts of these factors that will be informative to all users of satellite data. This contribution is framed by the widespread leveraging of satellite remote sensing for archaeology (e.g., [1; 2; 3; 4; 5; 6; 7; 8; 9; 10])--and that the trajectory for development is witnessing increasing spatial, spectral and temporal resolution, the potential to task data collection, and the proliferation of available data. While this is not yet a panacea for a range of reasons, including costs and, for example, the difficulties in calibrating and integrating different datasets from a range of Earth observation sensors [11], the rate of development is startling. Nevertheless, while recognising this trajectory, the lack of archaeological imperatives in the specification of data acquisition means that there are inherent compromises in primary survey data (see [12] for a comprehensive discussion of these factors for passive optical imaging). A central issue here is the capacity of remote sensing data to provide systematic and reliable data for archaeological management and research questions. This depends on many factors, not least of which is the ability to specify data acquisitions. Thus, while the capacity to image large areas with sub-metre ground sampling distance (GSD) optical sensors, to revisit regularly, and to specify conditions for acquisitions are all important, this remains largely beyond the reach of archaeology. Rather, archaeologists rely on using what is available in the market (inherently random, usually too expensive), what is possible to collect oneself (limited in coverage with inherent user bias), or what is freely available (medium to high spatial resolution or not specified for archaeology). Working with these available datasets, archaeologists have demonstrated that relevant information can be extracted from a range of remotely sensed data, including satellite data, at a variety of spatial and temporal resolutions for prospection, condition monitoring and land-use change [6; 7].