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Quasometry is precision measurement of celestial positions and apparentmotion of very distant extragalactic objects, such as quasars, galactic nuclei,and QSOs. We use this term to identify a specific area of research, themethodology of which differs from that of general astrometry. The main purposeof quasometry is to link the sub-milliarcsecond radio frame (ICRF) with theexisting and emerging optical reference frames of similar accuracy, constructedby astrometric satellites. Some of the main difficulties in achieving this goalare discussed, e.g., the extended structures of quasar hosts, apparent motionon the sky, optical variability, galactic companions, faintness. Besides thestrategic purpose, quasometry is undoubtedly useful for global astrometricsurveys, as it helps to verify or even correct the resulting reference frames.There are two options of using measurements of distant quasars in a globalastrometric solution: 1) hard constraints embedded in the fabric ofobservational equations; 2) {\it a posteriori} fitting of zonal errors. Therelative benefits and shortcoming of the two options are reviewed. A relativelysmall set of about 200 carefully selected reference quasars can go a long wayin improving the astrometric value of a space mission, if they are sufficientlybright, stable, fairly uniformly distributed on the sky, and are definingsources in the ICRF. We present an ongoing program at the USNO to construct aquality set of optical quasars with the required properties and to enhance theICRF with new sources in the areas where known, well-observed quasars arescarce.

Quasometry, Its Use and Purpose