EQUATORIAL DYNAMICS OBSERVED BY ROCKET, RADAR, AND SATELLITE DURING THE CADRE MALTED CAMPAIGN .1. PROGRAMMATICS AND SMALL-SCALE FLUCTUATIONS/

In August 1994, the Mesospheric and Lower Thermospheric Equatorial Dyn amics (MALTED) Program was conducted from the Alcantara rocket site in northeastern Brazil as part of the International Guara Rocket Campaig n to study equatorial dynamics, irregularities, and instabilities in t he ionosphere. This site was selected because of its proximity to the geographic (2.3 degrees S) and magnetic (similar to 0.5 degrees S) equ ators. MALTED was concerned with planetary wave modulation of the diur nal tidal amplitude, which exhibits considerable amplitude variability at equatorial and subtropical latitudes. Our goals were to study this global modulation of the tidal motions where tidal influences on the thermal structure are maximum, to study the interaction of these tidal structures with gravity waves and turbulence at mesopause altitudes, and to gain a better understanding of dynamic influences and variabili ty on the equatorial middle atmosphere. Four (two daytime and two nigh ttime) identical Nike-Orion payloads designed to investigate small-sca le turbulence and irregularities were coordinated with 20 meteorologic al falling-sphere rockets designed to measure temperature and wind fie lds during a 10-day period. These in situ measurements were coordinate d with observations of global-scale mesospheric motions that were prov ided by various ground based radars and the Upper Atmosphere Research Satellite (UARS) through the Coupling and Dynamics of Regions Equatori al (CADRE) campaign. The ground-based observatories included the Jicam arca radar observatory near Lima, Peru, and medium frequency (MF) rada rs in Hawaii Christmas Island, and Adelaide. Since all four Nike-Orion flights penetrated and overflew the electrojet with apogees near 125 km, these flights provided additional information about the electrodyn amics and irregularities in the equatorial ionospheric E region and ma y provide information on wave coupling between the mesosphere and the electrojet. Simultaneous with these flights, the CUPRI 50-MHz radar (C ornell University) provided local sounding of the electrojet region. A description of the campaign logistics and the measurements performed with the Nike-Orion instrumentation and their implications for turbule nce due to gravity waves and tidal instability in the mesosphere and l ower thermosphere (MLT) are presented here. From a study of electron d ensity fluctuations measured by rocket probes, we have found evidence for equatorial mesospheric neutral-atmospheric turbulence between 85 a nd 90 km. Furthermore, falling-sphere data imply that gravity wave bre aking was a source for this turbulence. Mean motions and the various p lanetary, tidal, and gravity wave structures and their coherence and v ariability are the subjects of a companion paper.