Indian Ocean. Further analysis of the Earth's gravitational field, coupled with other geological investigations, should answer many questions about the surface of the Earth in the next few years.

Progress was made in preparation for future satellite geodesy. NASA, Department of Defense (DOD), and the Department of Commerce jointly reviewed the requirements for geodesy and established broad requirements for a geodetic satellite program. A review

of these requirements has led to the consideration of the following program.

Future of satellite geodesy:

Optical tracking of many satellites.

Doppler tracking of Beacon EXPLORER.

Increased knowledge of:

Gravity field.

Station positions.

Optical tracking of ECHO, Air Density EXPLORERS.

Geodetic triangulation; Europe-Africa tie.

Flashing light satellite carrying laser reflectors and Doppler transmitter.

It is anticipated that part of the geodetic requirements will continue to be fulfilled by accurate tracking of many satellites which have other prime missions. This has been a very fruitful approach in the past as noted under the discussion of results of satellite geodesy. In addition, we will have special tracking devices such as Doppler or laser reflectors on satellites such as the Beacon EXPLORER discussed in the previous section on space environment. The addition of this equipment to the Beacon EXPLORER will allow this satellite to serve the dual purpose of investigating the space environment and geodesy. One of these spacecraft will be launched shortly into a polar orbit by a DELTA vehicle. A second spacecraft is being prepared for later launch into a low inclination orbit by a SCOUT vehicle.

Finally, there is still a need for special EXPLORER-type satellites for geodetic purposes. One such satellite under consideration will incorporate a flashing light and other tracking equipment developed and available from the ANNA satellite project. Under consideration also is a passive inflatable satellite for optical tracking for use in determining station positions and intercontinental ties.

Objectives

INVESTIGATION INTO THE NATURE OF THE UNIVERSE

The objective of these investigations is to understand how the forces, matter, and energy of the universe interact to generate the elements, stars, galaxies, and evolutionary processes observed by the astronomer (fig. 124).

The NASA program focuses on observations in the gamma ray, X-ray, ultraviolet, infrared, and radio wavelengths that do not reach the ground because of absorption by the atmosphere. Theory shows that the most important information on the birth, evolution, and demise of stars and galaxies is to be found in these various wavelengths. Thus, the theorist, working primarily with data obtained in the visible wavelengths, concludes that he has to build his present theories on the basis of the least important wavelengths as far as information content is concerned. These investigations are important in advancing our understanding of the fundamental nature of the universe in which we live. Indeed, it is in this area that scientists generally will agree there is the greatest chance of making discoveries that will lead to conceptual breakthroughs.

Progress

Significant results were obtained during the past year as follows (fig. 125):

1. Measurement of galactic noise intensity at 2 megacycles per second, 1.2 megacycles per second, and possibly 750 kilocycles per second.

2. Mapping of sky in soft X-rays. Probable discovery of new type of X-ray stars.

Progress toward future missions includes:

1. OAO: Prototype assembled and in test.

2. X-15: Stabilized platform and ultraviolet camera ready to photograph hot stars and nebulae.

29-063 0-64—pt. 1—9

3. Stratoscope II: System test flown twice successfully; mirrors nearing diffraction limited performance.

4. OAO: Design studies begun for infrared, X-ray, and gamma ray observing system, and small X-ray telescope being built to fly with ultraviolet spectrometer on OAO-Č.

5. Radio astronomy satellite: Design studies underway.

6. Geodetic satellite: Studies of the Earth's gravity field using data from the ANNA satellite.

7. Aerobee rocket: Stellar pointing control nearly operational.

8. OSO: X-ray and gamma ray telescopes being built for sky surveys.

Explorer status-Component system studies for the Radio Astronomy EXPLORER will be initiated early in 1964. If these study results are satisfactory, it is planned to start design and instrument work for the development of a satellite to conduct radio astronomy science. The first of these satellites is planned to be launched during 1966.

OAO spacecraft status.-The present OAO program consists of four spacecraft (fig. 126) with the first flight planned for 1965. To summarize the present status (fig. 127): the design and development of the OAO components and subsystems have now been essentially completed; the system testing of the prototype OAO (spacecraft plus experiment) has therefore begun and will continue through much of calendar year 1964; the system testing of the flight OAO will then take place in latter calendar year 1964 and the first part of 1965. 'Prior to calendar year 1963 the spacecraft structure and spacecraft thermal design had been qualified. During the past calendar year (1963) the

following has been completed: development and qualification testing of almost all of the many subassemblies (this program covers about 50 different subassemblies totaling more than 500,000 parts); all spacecraft subsystems including ground station equipment, has been functionally integrated and successfully operated; and the OẠO dynamic performance (stabilization, coarse solar pointing, fine solar pointing, roll-search and stellar acquisition, slewing, coarse pointing, and fine pointing) has been successfully demonstrated on air-bearing table tests. During calendar year 1964 the protoytpe system will be tested; the OAO-A system acceptance tests will be initiated; OAO-B components will be delivered and assembled; OAO-C fabrication will be initiated; and tests of the OAO launch vehicle peculiars will be completed.

OAO experimental status.-The telescopes for the first two OAO's are designed for observations in the ultraviolet. The third OAO will also observe primarily in the ultraviolet but will also have a telescope for X-ray observations. In addition to the use of OAO by the experiment developers, guest astronomers will utilize OAO observing time just as they do with Earth-based observatories.

OAO-A: The prototype package of the University of Wisconsin experiment for OAO-A has been delivered and the functional operation with the spacecraft has been successful. The qualification testing will take place in the first part of calendar year 1964. The delivery of the Smithsonian Astrophysical Observatory prototype experiment will be made in the first part of 1964. The delivery and test of the flight systems for OAO-A will take place in calendar year 1964.