In the history of humankind only three spacecraft have ever ventured into interstellar space [2]. How- ever, none of them have been equipped for proper exploration of interstellar space, all of these five spacecraft were equipped for exploring the outer planets and objects of the solar system but not for interstellar space and/or the heliosphere. In part due to this lack of in-situ measurements of the inter- stellar medium and the heliosphere, not a lot is known of these areas. This report aims to provide a detailed overview of the concept of an interstellar heliosphere probe to investigate the heliosphere and the interstellar medium. This report will examine the requirements that are needed for such a spacecraft and explain why these requirements exist. Moreover, a component level description of the various subsystems typically involved in spacecraft manufacturing will be provided. With these subsystems, estimations of the mass, cost, power and data will be given when appropriate in an overview of all the subsystems.

The goal of project Altus is to do an in-situ investigation of Polar Mesospheric Clouds (PMCs). These clouds form around an altitude of 84 km, and only for 60 to 80 days per year, during the summer. Normally, these clouds only form in the polar regions, from around 50◦ latitude north and south. Recently, however, PMCs have been observed as low as 40◦ north. There are theories linking this change in location, and other unexpected behaviours of PMCs, to climate change. However, further research is still required to confirm these theories. As these changes are happening at a slow rate, a database of PMC measurements would be extremely beneficial to track indicator values over time. Project Altus sets out to bridge this knowledge gap by taking regular measurements of PMCs over an extended period of time.