1. The question is not what is possible
After defining what a successful first year looks like, the next obvious question is: what object do we actually try to keep first? This is where the project stops being philosophy and starts being a shopping list. The object must be small enough to catch, interesting enough to justify the attempt, and well-enough known that we can plan without inventing too many variables.
Arthur C. Clarke’s Rendezvous with Rama is the perfect companion here. The whole novel is about approaching an unknown object, matching its spin, figuring out its shape, and deciding what to do with it. The keeper’s first object will be far smaller and far less exotic than Rama, but the emotional shape is the same: a thing is moving through space, and we want to make it ours.
2. Candidate one: a spent upper stage
There are hundreds of spent rocket bodies in Earth orbit. They are large, metallic, trackable, and in many cases decades old. A spent Centaur or Briz-M has known dimensions, known materials, and no owner who is likely to object to a demonstration docking. The downside is that most are in LEO or GEO, not on energetic orbits that teach us much about asteroid capture. Catching a dead rocket stage proves rendezvous and berthing, but it does not prove we can handle a natural rock.
Still, for a first year, that might be exactly right. The goal is to learn to grab something without also learning how to survive an unknown regolith structure.
3. Candidate two: a minimoon
Minimoons are small asteroids that wander into Earth’s neighborhood and loop around for months or years before escaping. They are scientifically perfect for the keeper: natural composition, temporary capture, and a clear deadline. If we can reach one during its visit, we get to practice everything that matters for later interplanetary capture.
The problem is timing. Known minimoons are rare and short-lived. 2020 CD3 escaped after a few years. 2024 PT5 was available only for a couple of months. A keeper that depends on catching a minimoon is a keeper that spends most of its time waiting. That is not necessarily bad, but it is a different business model than a continuous service.
4. Candidate three: a small near-Earth asteroid on a friendly orbit
Instead of waiting for Earth to hand us a visitor, we could go out and meet one. Many near-Earth asteroids have orbits that are energetically cheaper to reach than the Moon’s surface. The catch is the word energetically. Cheaper than the Moon still means years of transit, precise navigation, and a long list of unknowns about the target.
This is the most ambitious first object and probably the wrong one for year one. But it is worth keeping on the shelf, because the keeper only makes sense as a long-term project if it can eventually handle objects that were not already convenient.
5. A tentative ranking
If I had to choose today, the order would be:
- Spent upper stage in LEO or GEO for the first demonstration. It proves the mechanical stack and the regulatory tolerance.
- Minimoons and temporary capture objects for the second demonstration, if one appears during the operational window.
- Small NEA on a friendly orbit only after the first two have taught us what we do not know.
This ranking values learning over spectacle. It also admits that the keeper may need to spend its first year being ready, not doing.
What this changes
- The keeper’s first demonstration target is narrowed to spent rocket bodies as the most credible learning object.
- Minimoons remain the emotional and scientific ideal, but their rarity makes them opportunistic rather than planned.
- Small NEA capture is deferred until the keeper has a proven rendezvous, berthing, and operations stack.
- The next leisure entry can explore what a spent-stage demonstration mission actually looks like in mass, time, and cost.