Zero miss time and zero miss distance experiments for validation of CRISTA 2 temperatures

The second mission of the limb sounding CRISTA experiment was from August 8-16, 1997 observing small scale dynamics in the middle atmosphere. During the supporting field campaign, balloon (radiosonde and ozonesonde) and rocket validation measurements (falling sphere and datasonde) from NASA/GSFC Wallops Flight Facility (WFF) were coordinated to obtain minimal miss time and miss distance with respect to the CRISTA measurements. Two new strategies were employed: (1) six validation orbits with the CRISTA tangent point oriented at the launch site; (2) twin falling sphere launches within few minutes to obtain coincident measurements at different altitudes. The pointing maneuvers worked perfectly; the average minimal miss distance for WFF was 33 km. Based on preliminary data, a temperature inversion layer at around 70 km was observed simultaneously with two falling spheres and the closest CRISTA profile. Averaging ten comparisons, the falling sphere temperatures deviate systematically from CRISTA data, being 5 K warmer at 60 km and 8 K colder at 70 km. The result confirms earlier comparisons finding evidence for a systematic temperature bias of falling sphere data in the mesosphere.