As ESA’s Hera mission for planetary defence probes the Didymos twin asteroid system, it will be joined by a pioneering pair of breadbox-sized ‘CubeSats’. Juventas will perform radar soundings while Milani will image the bodies in a wider range of colours than the human eye can see, prospecting the mineral makeup of individual asteroid boulders.

Hera will reach the Didymos system in 2027, to survey the aftermath of a collision by NASA’s DART spacecraft with the smaller of the two asteroids, Dimorphos. Hera will carry with it two ‘CubeSats’ – nanosatellite-class missions based on standardised 10-cm boxes, making maximum use of commercial off the shelf systems.

Which brings to light a compromise between our positions here. Why can’t future impact tests like DART include all of HERA’s tech as well? Have a HERA sized probe that detaches from a DART type probe several weeks before impact, and do immediate post impact surveillance. Include a swarm of cubesats and other micro probes to do a deep study of the target.

Or perhaps even have the HERA type probe arrive first by detaching months earlier, giving it a few weeks to survey the target before impact? Obviously the DART type probe would have to be scalable for different size targets, but the HERA type probe and cubesats could be essentially production line off the shelf units.

When the data is analyzed, we will understand how this particular type of asteroid is affected by a mechanical collision. But we will not know whether it is a typical asteroid, or what other asteroids are like, or how they will react to similar collisions.

For example, I would really like to know if the primary in that system was of similar composition to the orbiting body. That might give us some clue as to how the whole system formed. In other words, an asteroid exploratory mission is very valuable, we should have spent time flying around the system making observations and measurements, rather than just crashing into one of them.