SOUNDING ROCKETS

As previously mentioned, the solar eclipse operation on 7 March 1970 was the biggest single sounding rocket project conducted during 1970. Thirty-two rockets were launched successfully from Wallops Island, 17 of these during a 20-minute period at the time of the eclipse. Other rocket flights were made to check out instruments of the type to be flown in 1972 on the solar telescope, ATM, of Skylab.

Sounding rockets in stellar astronomy again have brought back a wealth of information. One of the more exciting results was the demonstration that conditions are right in some parts of our galaxy for forming new stars. Previous measurements had always indicated that the density of matter was just too low for the gravitational construction of interstellar clouds into a new star. The additional matter, increasing the cloud density, was found to be in the form of molecular hydrogen which had not been detected previously. Another discovery was that quasars may be emitters of X-rays. Two quasars (3C-273 and NGC-5128) appear to emit X-rays in the 1.0 to 10 thousand electron volt energy range. If quasars are at cosmological distances, as is generally supposed, then the total energy production must be even larger than the extraordinary amount that was observed just in the radio region.

Sounding rockets are our primary means for measuring vertical profiles of geophysical parameters, or for obtaining data below 80 miles where satellites require a very large propulsion capability to survive. They are consequently irreplaceable in space physics where they are often used in conjunction with satellites to perform coordinated investigations.

In one experiment, a Javelin sounding rocket was launched to search for energetic, neutral hydrogen in Earth's upper atmosphere. This experiment had been developed in order to search for a very weak neutral component in the solar wind. To our surprise, a large flux of neutral hydrogen was found coming from the general direction of the Sun which is of comparable intensity to the solar wind itself. This result is both perplexing and exciting; only a small fraction of the solar wind should be neutral hydrogen, and most of the hydrogen should be photoionized before it could travel from the Sun to Earth. It may be that much of the solar wind is neutralized by charge transfer in the upper magnetosphere. If confirmed by subsequent experiments, this finding would require major revisions of our models of solar terrestrial relations.

AIRBORNE RESEARCH

In June 1970 a small electron accelerator was flown on an Aerobee 350 rocket (Chart SG71-2676). It injected short bursts of energetic electrons into the lower edge of the inner radiation belt. The electrons traveled over 10,000 miles along Earth's magnetic field lines before returning almost to their point of origin. They were observed repeatedly as they bounced along the field lines between the Southern and Northern Hemispheres. This behavior was expected. The important new information is that the energy of many of the electrons changed while the beam spread and low frequency electromagnetic waves were generated. Initial clues about the behavior of trapped electrons in the inner radiation belt has been obtained with this rocket, and a new tool for future research has been proved.

Instrumented jet aircraft provide platforms for observations which cannot be accomplished from the ground and yet do not require the higher altitudes of balloons, sounding rockets, and satellites. Airplanes have great operational advantages because the scientist may conduct his observations in person, observations may be carried out over any geographic area, and the instruments can be easily maintained, modified, and returned to a ground laboratory when necessary. These advantages are similar to those expected from the Space Shuttle, and the Airplane Program can provide operational experience that is applicable to the Shuttle Program.

Infrared astronomy research is the primary objective of the physics and astronomy airplane observations. Jet aircraft can fly above most of the atmospheric constituents that absorb far infrared radiation, permitting observations of celestial objects at these wavelengths. Although the technique has been used for only a few years with simple equipment and a small 12-inch telescope, new and fundamental results have already been obtained. The data indicate that we have observed stars in the actual process of formation, unexpected sources of energy at the center of our galaxy, and distant galaxies which radiate strongly in the infrared. Thus, observations from jet aircraft show promise for yielding answers to problems about the birth of stars and the evolution of galactic systems. As discussed previously, observations of a nova have been made in the far infrared, and the infrared data are being correlated with visible data from the ground and with ultraviolet observations made with OAO 2.

The results obtained so far have clearly demonstrated the value of infrared airplane observations and also show the need for more sensitive and more advanced observing equipment. A tremendous increase in capability will be possible with a 36-inch aperture Cassegrain telescope now being built for use aboard the C-141A aircraft (Chart SG71-2663). The increased telescope size, pointing capability, and longer duration at altitude will allow more detailed studies of infrared sources, and also permit observations of very faint objects on a new scientific frontier.

BALLOONS

The versatility of the oldest space flight tool, the balloon, was proved again during 1970. About 60 balloon flights were conducted in support of the Physics and Astronomy Programs during 1970. Of special interest were several flights in support of major space projects that carried payloads weighing several tons.

In order to help in the development and test of the HEAO instruments, a three-ton cosmic ray calorimeter was flown to 110,000 feet with a balloon that was about 500 feet in diameter (27 million cubic feet in volume). The instrument on this flight carried out the first direct United States measurements of cosmic rays with energies above 100 billion electron volts. Chart SG71-2674 shows the launch balloon being filled with helium. The main part of the balloon is stretched out along the ground. The insert shows the payload.

Even visible light pictures of stellar objects that can be obtained with large ground-based telescopes are degraded substantially by the atmosphere through which the light has to travel. One of the objectives of a balloon project, called Stratoscope, is to fly telescopes above most of the atmosphere and thus obtain stellar pictures that are not degraded by the atmosphere but are limited only by the nature of light and the laws of optics. A 36-inch telescope, Stratoscope 2, was flown the night of 26 to 27 March 1970. More than 200 pictures were taken of Uranus, Jupiter, a satellite of Jupiter, and the nucleus of the Seyfert Galaxy, NGC-4151. The latter observation proved to be the most interesting. It showed that the nucleus of that galaxy is so small by astronomical standards (at most 12 light years in diameter) that if this nucleus is composed of stars, then collisions between these stars should be occurring every few months. Thus, either the matter in the nucleus of this galaxy is not organized in stars, or else a new process has been found that affects the energy production in a galactic nucleus.

The NASA Balloon Program uses to good advantage the ballooning capabilities of other agencies. For instance, most of the balloons were launched from Palestine, Texas, by the National Center for Atmospheric Research (NCAR), others by the Air Force at Holoman Air Force Base. New Mexico. NASA also participated in a balloon expedition to Fort Churchill, Canada, that was conducted by the Office of Naval Research (ONR).

SUPPORTING ACTIVITIES

A large number of diverse, small research efforts are needed in support of our flight program (Chart SG71-2679). Concepts for new missions must be studied to establish the feasibility and approximate schedule and cost before a program can be approved. Ideas for new or improved measurement techniques must be explored in the laboratory before being assigned to flight, and ground-based measurements must be performed for correlation purposes in order to interpret the data. Theories must be developed to explain the phenomena observed and to predict possible applications of newly discovered processes. Long-lived space missions produce a very large amount of data, and each observation is unique. A great deal of analysis effort is required in order to recognize common features of different events and to determine whether the observations agree with one of the various theories that have been proposed.

LARGE SPACE TELESCOPE (LST) STUDIES

The major effort in advanced studies will be concentrated on the LST. The results already obtained with the OAO, and those expected in the future, will extend our view in the ultraviolet beyond our own galaxy. In order to take full advantage of the unique capabilities of scientific satellites for exploring the universe in the optical portions of the electromagnetic spectrum, we are studying telescopes comparable in size to the largest existing ground-based instruments (two meters and greater in diameter), and exceeding their performance by an order of magnitude.

The LST would make a dominant contribution to our knowledge of cosmology-to our understanding of the content, structure, scale, and evolution of the universe. What is its curvature? How far does it extend in time and distance? What are quasars and other known peculiar astronomical objects? Perhaps most importantly, it may detect other rare and previously unobserved phenomena at the edges of our universe.

Past work has established the basic feasibility of the LST and the desirability of taking into account the Space Shuttle capability in the design philosophy of the system. Accordingly, an LST Task Team has been established in NASA Headquarters with participation by the Office of Manned Space Flight, Office of Advanced Research and Technology, and the Office of Space Science and Applications. This team will be supported by a scientific steering group composed of both academic and in-house NASA scientists.

Past studies have been carried out by industry and NASA field centers. One of the concepts studied, with regard to the feasibility and interfaces with the manned systems, is the configuration shown in Charts SG71-15154 and SG71-2664. This was designed to be launched either by the Titan or the Shuttle. The construction uses modular subsystems to permit easy repair and updating in space.

One of the difficult requirements to be met is that the shape of the main mirror should not depart from its ideal shape by more than one-millionth of an inch. Normally, deformations of the mirror by Earth's gravitational forces are considerably larger than this figure. It may be possible that actual tests in space can be performed more easily than laboratory simulation.

The Space Shuttle would be one means by which the testing could be accomplished. It could take the telescope into space, test its actual performance, and return it after a few days' operation. Final adjustments and polishing could then be made in the laboratory to attain the desired performance.