2.1 GEOTAIL The joint Japan/US GEOTAIL satellite inaugurated the ISTP Program with its launch on July 24, 1992. GEOTAIL carries two US experiments, and five Japanese experiments, three of which have US co-investigators. The GEOTAIL instrumentation provides excellent measurements of plasmas, energetic particles, plasma waves, electric and magnetic fields. During the initial phase of 28 months (extended from the original 18 month plan to await the launch of WIND), GEOTAIL carried out the most comprehensive survey ever made of the distant magnetotail out to 200 RE. In late 1994, GEOTAIL was transferred to a new orbit designed to study the magnetosphere between 10 and 30 RE in the equatorial region, a region of critical importance for magnetospheric dynamics and of primary scientific interest to Japanese scientists. In its current orbit, GEOTAIL also routinely samples the magnetopause and bow shock boundaries, providing advantageous configurations of ISTP/GGS spacecraft for these studies.	Figure 1.2 Geotail and its instruments
2.2 WIND The WIND spacecraft was launched on November 1, 1994 into a double-lunar swingby orbit with maximum apogee of 250 RE that keeps it upstream of Earth most of the time. From this vantage point, WIND is able to detect the properties of the solar wind plasma before it reaches the Earth. A full complement of field and particle instruments is available to sample the interplanetary medium with unprecedented detail. Furthermore, remote sensing of radio and plasma waves with 2-D direction finding is possible. WIND also carries two gamma-ray spectrometers that provide the first high-resolution spectroscopic survey of cosmic gamma-ray transients, including those from solar flares, x-ray novae, and gamma-ray bursters.	Figure 1.3. Wind and its instruments.
2.3 POLAR POLAR was the last ISTP spacecraft to be launched on February 24, 1996. This successful launch completed the implementation of space and ground-based assets for ISTP. The spacecraft orbit has an apogee of 8 RE and perigee of 0.8 RE altitude, and an inclination of 86o. The initial apogee was at 68o north and has been precessing towards the pole at a rate of about 16o per year. POLAR carries 11 science instruments plus an engineering experiment. Three imagers provide tri-spectral imaging for the first time in ultraviolet, visible and x-ray wavelengths; these are mounted on a despun platform that has one degree of freedom for motion to optimize viewing of the aurora and other targets. Beside the imagers, the spacecraft carries five types of charged particle detectors which sample electron and ion populations, including species identification, from thermal to relativistic energies. The engineering experiment reduces the charge on the spacecraft so that, for the first time, thermal ions can be measured in low plasma density regions of the polar magnetosphere. POLAR’s electric and magnetic field instruments include dual high resolution fluxgate magnetometers, and the first successful triaxial electric field instrument in the magnetosphere, which also contains burst-mode data capability for ultra-high time resolution. The array of wave sensors allows complete measurement of plasma waves, and a wideband telemetry link allows the acquisition of high time resolution data. A special loss cone charged particle imager on the despun platform complements the body-mounted charged particle experiments which in conjunction with the wave instruments, allow extensive studies of wave-particle interactions.	Figure 1.4. Polar and its instruments.