The temporal evolution of the wake of a conducting body is studied experimentally in a p• plasma device. Three--dimenzional measurements of the plasma potential, dermiry, particle energy distribution, and ion currents are measured throughout the near-and mid-wake region• during the wake formation. It is found that the potential behind the conducting body is initially negative. This negative potential is caused by the higher mobility of the electrons, allowing them to liow into the ion free wake region. The negative potential in the wake region induce• an electric field that pulls ions into the region behind the conducting body. However, the dominant factor in determining the length of the near wake is the thernml energy spread of the ions. At later time•, as the sheath forms around the conducting body, ion• are deflected by the potential gradieni in the sheath region. This deflection, in addition to the thermal energy spread of the ions, determine• the length of the near wake. platforms must be understood in order to correctly interpret the data from diagnostics and sensors.Because of their importance, the study of plasma wakes has long been an area of interest in space physics. Several authors, including Sarnir et. al. [1979, 1980, 1981, 1986], and Medved [1969] have investigated the problem of the environment of a satellite in the ionosphere. Sarnir et. al. [1986] and Henderson et. al. [1967] observed wave excitation in the wake region of satellites, while Troy et. al. [1975] observed temperature enhancement in the wake region. All of these investigators dealt with the interactions of small spacecraft with the ionosphere. The wake region of large space structures such as the space shuttle has also been investigated, with Riatt et. al. [1987] and Murphy et. al. [1986] having investigated the plasma parameters in the wake region, while lngsoy et. al. [1985] has studied the energization of the plasma. In addition, Tribble et. al. [1989] have investigated plasma disturbances due to the motion of the space shuttle. These observations were limited to measurements of the electron density and temperature in the near wake of the space shuttle. In waz flown on the space shuttle as part of the Spacelab 2 mission. This satellite was designed to make comprehensive in situ measurements of the plasma density, temperature, and turbulence in the near, mid, and far wake of the space shuttle. Tribble et. al. [1989] reported measurements of these parameters and related the turbulence spectrum to the gradients of the temperature and density. Because of the difficulties in obtaining comprehensive free wake region, ion density enhancement in the mid wake and made predictions of disturbances in the wake region while the work of Gurevich is an excellent review of ionospheric plasma flow around objects. Liu predicted the generation of ion-acoustic waves in the wake region while Troy and coworkers showed that experimental evidence of electron heating could be explained by wave-particle interactions. 13,985 13,986 MEASSICK ET AL.: WAKE FO...