Abstract
The atmosphere within Earth’s Geospace System, herein taken to be the region from the upper mesosphere (65 km) to the exobase (~ 600 km), is cooling and contracting due to increasing carbon dioxide in its lower regions. These changes will affect many aspects of future orbiting satellite operations in Geospace. Recent assessments place the value of the orbiting-satellite-driven “space economy” at US $1.8 × 10 12 within a decade. To assess Geospace change in a quantitative way that can facilitate a sustainable space economy, a Geospace System Observatory (GSO) is essential. The GSO would generate Geospace Data Records (GDRs) from which the rate and long-term extent of Geospace change can be determined with sufficient statistical significance to expedite confident international decisions and agreements regarding satellite and other operations in Geospace. In this paper, we present specific attributes of measurements intended to serve as GDRs. Foremost among these is high absolute accuracy that is driven by the need to limit trend error to a fraction of the anticipated trend magnitude over multiple instruments spanning decades. High accuracy also provides the statistical significance to enable confident decisions and shortens the time required to confidently detect trends. Other GDR aspects (record length; overlap/continuity; SI traceability) are also discussed. Examples of a variety of trend errors from current and past satellite sensors are given as a guide to GSO design requirements. A method for developing Level 1 design requirements for the GSO, used for developing systematic satellite observations for the troposphere, concludes the paper.