2017.A.4.5. Planetary CubeSats, nanosatellites and sub-spacecraft: Are we all talking about the same thing?

Author(s)

Frank Crary (1)

University of Colorado, United States of America

Session

A.4

Keywords

Design requirements, autonomy, risk posture

Abstract

In the past few years, the idea of planetary CubeSats has gained considerable attention, with several in development, funded concept studies and even statements that including CubeSats may become a regular part of planetary missions. However, it is not clear what these efforts consider a CubeSat. Frequently described as a spacecraft with a 10 cm x 10 cm x 10 cm x N size, CubeSats are really defined by far more than their form factor. Other critical aspects include, but are not limited to, the use of commercial, off-the-shelf components, a standardized deployment mechanism (thereby greatly simplifying the interface with the launch vehicle and primary payload) and a risk posture which accepts that failure is an option, but harm to the primary payload is not. In fact, traditionally, CubeSats have no interaction with the primary payload at all. Many of the advantages of CubeSats result from the synergy of these characteristics. In contrast, a 10 cm x 10 cm x 10 cm x N planetary spacecraft, developed according the requirements and practices of a major planetary mission, would not be a CubeSat. It could be a valuable and useful planetary mission, but it would lack many of the benefits commonly associated with CubeSats. Small spacecraft can also benefit from association with a larger mission, for example remaining attached during the heliocentric cruise phase and only being deployed at the destination, or having a larger mission act as a telecommunications relay. However, this imposes a burden on the primary mission and requires interactions normally avoided by CubeSats. At some point, such a spacecraft might be more accurately described as a subspacecraft, i.e. one of the primary spacecraft’s instruments which simply happens to be physically detached. This presentation will attempt to describe the various characteristics, expectations and tradeoffs associated with the distinction between CubeSats, nanosatellites and subspacecraft.