Anna, Apollo, Cosmos, Courier, Diapason, Discoverer, Echo, Explorer, Gemini, Pace, Plumb, Poke, Posse, Prize, Probing, Prod, Quantify, Quest, Ransacking, Rate, Read, Research, Rummage, Sample, Satellite, Scrutiny, Search, Searching, Sift, Sifting, Sister, Size, Sound, Sounder, Spacecraft, Span, Sputnik, Stalk, Stalking, Step, Study, Survey, Triangulate, Value, Weathercock, Weigh, Luna, Mariner, Mercury, Midas, Nimbus, Pegasus, Pioneer, Proton, Ranger, Relay, Sputnik, Surveyor, Transit, Vanguard, Viking, Appraise, Appreciate, Assay, Assess, Barometer, Calculate, Calibrate, Caliper, Compute, Delving, Detection, Dial, Dig, Divide, Dragnet, Enquiry, Estimate, Evaluate, Examination, Examine, Exploration, Explore, Fathom, Feeler, Forage, Frisk, Gauge, Go, Graduate, Hearing, Hunt, Hunting, Inquest, Inquiry, Inquisition, Investigate, Investigation, Legwork, Measure, Meter, Nurse