wake, than the smooth cylindrical structure expected at this distance. Knowledge of the tail helps scientists understand the relationship between the magnetic field of the earth and the solar wind. The three Pioneer spacecraft transmit a daily "space weather" report to the Environmental Science Services Administration and the North American Air Defense Command (NORAD) to assist in forecasting.

The next Pioneer launch is scheduled for November. The spacecraft was assembled and completed earth test phases satisfactorily. It will

carry instruments similar to those on Pioneers VI, VII, and VIII and will complement their observations with studies of magnetic fields, plasma, and high energy particles.

Earlier Spacecraft

In May, OGO-IV (launched in July 1967) completed ten months of successful operation. The spacecraft is in a low, nearly polar orbit (250 to 560 miles) where it studies the relationships between solar phenomena and solar radiations and the earth's environment during a period of increasing activity of the sun.

Explorer XXXIV (orbited in May 1967 with a planned lifetime of a year) survived a threat to its continued operation this May when it passed into earth's shadow for four hours. While there, the satellite's temperature fell far below that for which its systems and subsystems were designed, but it emerged from the shadow to continue functioning as before and was ready to transmit data for a second year. As a result, the launch of a similar spacecraft-Interplanetary Monitoring Probe-G, IMP G-being readied to replace it could be postponed until March 1969.

Explorer XXXV, launched in July 1967, provided data on the behavior of the solar wind in the vicinity of the moon and confirmed that the moon has a very small magnetic field, if any.

Scientists have concluded after analyzing data from Orbiting Solar Observatory III (OSO-III launched March 1967) that the center of this galaxy is a source of 50 million electron volt gamma rays. This gamma ray intensity is much greater than expected. Information supplied by all of the Orbiting Solar Observatories to date, including data transmitted by OSO-IV orbited in October 1967, has substantially increased scientific knowledge of the sun, because these spacecraft carry experiments able to observe and measure solar radiation that cannot penetrate the earth's atmosphere and be studied by earth-based observers.

Experiments aboard Applications Technology Satellite I (ATS-I), launched in December 1966 into a 22,300-mile geostationary orbit over the Equator, measured trapped electron fluxes and magnetic fields before and during a magnetic storm on January 13-14, 1967. The measurements showed that the spacecraft had crossed in and out of the region of trapped electrons and part of the time was outside the magnetosphere where it was exposed to energetic solar particles. This information will help in planning for the safe passage of astronauts traveling in a similar orbit through these regions. The finding is supported by OGO-III experiments.

Sounding Rockets and Balloon Flights

To continue its studies of the lower ionosphere, airglow, cosmic dust, stellar ultraviolet and X-radiations, auroras, and solar physics, NASA launched 71 scientific sounding rockets. In addition, it sent aloft 26 balloons carrying instruments primarily for astronomical observations. Among the significant sounding rocket launches were

• Test flights of the boosted Arcas II and the single-stage Tomahawk vehicles, which were then added to the stable of operational rockets.

The second flight of the Rice University (Houston, Texas) "Twins" experiment including instruments being developed for the Owl satellite.

• A test flight of the Solar Pointing Aerobee Rocket Control System (SPARCS) with a pointing accuracy of 5 to 10 arc seconds.

• Test flights of Injun V experiments on a Javelin vehicle.

• Second flight of a solar physics experiment using the Solar Capture and Tracking (SCAT) pointing control system with an accuracy of 5 to 20 arc seconds.

Operationally successful flight of the high altitude (850 to 1200 miles) Astrobee 1500 rocket.

• Flight of the bioscience "Gravity Preference" experiment.

• Five flights of X-ray astronomy experiments using the Stellar Tracking and Positioning (STRAP) pointing control system with an accuracy of 5 to 20 arc seconds.

Airborne Aurora Expedition

A six week-study of the Aurora Borealis (the Northern Lights) and the polar cap airglow was made from a NASA jet airplane during the first three months of 1968 in a series of flights from Canada's Fort Churchill Research Range. The flights, which extended from Greenland to Alaska at altitudes of 32,000 to 40,000 feet, carried out the most intensive studies of the Northern Lights ever made. Thirteen experiments were aboard the plane-spectrometers, photometers, cameras, radio receivers, and a magnetometer-and 14 universities and research organizations participated.

Flying beneath auroras at 550 miles an hour, the aircraft canceled out the speed of the earth's rotation by flying against it and holding a constant position on the night side of the earth opposite the sun at latitudes above 60° North. Some of the flights afforded continuous views of auroras for more than five hours, and frequent trips were made to the north Magnetic Pole north of Greenland. In the course of the study, 40,000 auroral photographs were taken, and 180,000 feet of

magnetic tape recorded instrument readings from above five-sixths of the atmosphere of the world.

During many of the flights, experiments carried by the plane were coordinated with auroral and polar cap phenomena experiments of OGO-IV. Three times the aircraft crossed a spot in the northern magnetic field at the same time that the spacecraft crossed a complementary spot in the southern magnetic field. On six passes of OGOIV over the northern hemisphere, the plane measured a group of auroras from below 40,000 feet while OGO-IV measured the same group from above that height. Also, some of the flights were coordinated with launches of scientific sounding rockets from the Fort Churchill Research Range.

This airborne aurora expedition proved for scientists the value of the high altitude observatory jet aircraft and showed that it could "stop time" for observations near both poles.

Surveyor

Lunar and Planetary Programs

Surveyor VII, the last in the series of lunar soft landers, was launched on January 7 and two days later landed on the moon, about 18 miles north of the rim of the crater Tycho. (Fig. 2-3.) Earlier Surveyors were sent to lunar mare regions to scout potential landing sites for Project Apollo astronauts in the moon's equatorial belt, but this Surveyor was directed to an area of entirely different geological characteristics the rugged, rock-strewn, ejecta blanket just north of this large ray crater. This hazardous region was chosen because it is well within the lunar highlands far removed from the mare basins previously investigated and is believed to be covered with debris excavated from deep beneath the surface of the highlands when Tycho was formed.

During the first lunar day (14 earth days) the spacecraft transmitted 21,038 TV pictures. (Fig. 2-4.) It survived the extreme cold of the two-week lunar night and sent back 45 more pictures in the course of the second lunar day. The alpha-scattering (chemical analysis) instrument, after completing a background count in the intermediate position, failed to touch down on the lunar surface. Through a series of intricate maneuvers, the surface sampler was used to force the alphascattering instrument all the way down. The surface-sampler was then used to pick up the alpha-scattering instrument after its first chemical analysis was completed and move it to two other locations for further analyses. These delicate operations demonstrated the versatility of the surface-sampler as a remote manipulation device and the precision with which its operations could be controlled from the earth.

From samples of the undisturbed lunar surface, a lunar rock, and an area dug up by the surface-sampler (fig. 2-5), about 66 hours of chemical composition data were obtained during the first lunar day. Thirty-four more hours of data were provided by the surface-sampler the second lunar day. This device dug numerous trenches, conducted static and dynamic bearing strength tests, picked up rocks, fractured and weighed a rock, and performed various other manipulations of