Echoing myself from Discord, we can use the
WISE mission and
2016 WF9 as calibration.
WISE is a 660kg spacecraft, which we can approximate as 1t (and therefore SM+2), mounting a 10-system-sized telescope (effectively normal-sized for SM+4, therefore TL-5, therefore +3 bonus).
If we assume maximum time spent (30 minutes, +5), that WISE instead of scanning the whole sky 'zooms in' despite lack of an actual target (another +3), we get another +8.
Distance to target is at least 0.341AU (-63), size is at most a kilometre (+16).
Therefore, the total modifier is +16 (SM) +5 (time) -63 (range) +3 (sensor) + 3 (zoom) +24 (in space) +10 (in plain sight), for a final modifier of -2 [1], which does sound like a reasonable order of magnitude.
[1] And potentially a bit worse, since I'm assuming maximum size and minimum distance. Then again, you're probably dealing with skill levels of ~14-15.