In Icarus (the ‘international journal of Solar System science’) for vol. 424, Dec 2024:
Föhring, D. Conversi, L. Micheli, M. et al. Site selection for the second Flyeye telescope: A simulation study for optimizing near-earth object discovery Art 116281 .116281
Laurent-Varin, J. James, T. Marty, J-C. et al. New gravity field of comet 67P/C-G based on Rosetta’s Doppler and optical data Art 116284 .116284
Most NEOs (Near-Earth Objects) are discovered by three programs (Catalina Sky Survey, Pan-STARRS, and ATLAS), all US-founded (though ATLAS has expanded to foreign sites). But Japan, Europe (collectively), and Korea are not asleep. The (first) Flyeye telescope, or NEOSTEL, is largely built and due for first light any period now. That Flyeye telescope is on Monte Mufara, Sicily. Where should additional units be placed? The original NASA plan was for four telescopes, to span the Northern/Southern Hemispheres, and day/night cycles via diversity in longitude. What we actually got was Pan-STARRS, both in Hawaii, and within a stone’s throw of each other. Oh well, at least Hawaii is at a low enough latitude that there’s some Southern coverage. The Europeans are not making that ‘mistake’- putting rigor to the question of a second (hopefully third) observatory. Even with the Vera Rubin Observatory, now in early testing, a second Flyeye in Chile still makes sense. Based on VRO coverage, that mighty ‘scope still requires 3-4 nights to cover the sky, then start revisits. Föhring et al. find that in that three days, a complementary telescope can still find non-redundant NEOs. And that’s assuming perfect weather, no mechanical failures or other downtime. Given Flyeye 1’s Northern, Mediterranean site, a Flyeye 2 near Vera Rubin in Chile still works.
Sometimes, though, there’s just no substitute for a probe. Density measurement, for one, is possible with precision astrometry- we can gauge the pull of some massive body, tugging a lesser body. In many cases, however, there’s no convenient body-pairing orbital motion to give us that gravity number. In the case of a space mission, no probe ever launched is comparable in mass to even the small asteroids. Having a probe fly past (or orbit, certainly) an asteroid or comet can get us some numbers. Rosetta certainly orbited comet 67P/Churyumov-Gerasimenko. At issue are the odd, complex shape of the comet nucleus, and its overall low density (lots of empty space between dust aggregates). With this hindsight, Laurent-Varin et al. attempt a better gravimetry of the body, including local highs and lows.