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3. Very old rock material, representing pieces of the lunar crust formed very soon after the formation of the Moon, is evidenced in several samples.

4. Soil "ages" from all Apollo and Luna missions are clustered in the range 4.2-4.7 billion years.

5. Rock age dates obtained on Apollo 16 are very intriguing because among them are ages which fit in the time period 3.9 and 4.6 billion years ago, a period previously represented almost as a gap in the lunar time scale.

6. An Apollo 16 soil sample taken from the bottom of a trench where it was protected appears to contain a relatively high abundance of the materials, water, methane, and hydrogen cyanide, thought to be the remains of interaction of the Moon with a comet.

7. Seismic velocities at the Descartes landing site are characteristic of breccia terrain and support the contention that there are no layered volcanic rocks near the surface at this site.

8. We can now say with high confidence that internal moonquakes arise from great depth, 800-1,000 km, indicative of a relatively cool, rigid interior at that depth.

9. Preliminary analysis of an impact event, which occurred on the lunar farside last July and sent seismic waves through the Moon, shows evidence for the possible presence of molten rock in the deep interior of the moon (below approximately 1,000 km), possibly in association with a small lunar core.

10. During times of solar flare activity, there is an increased abundance of solar iron and other heavy elements leaving the Sun at low energies relative to the light elements such as hydrogen and helium.

11. The western maria are unusually high in near surface radioactivity.

12. Measurement of the potassium-to-uranium ratio indicates that the entire lunar surface appears to be characterized by a value from 2,500 to 5,000, clearly distinct from a terrestrial value of about 10,000. This adds weight to the argument that the Moon did not fission from the Earth.

13. An increase in the amount of polonium (a product of the radioactive decay of radon) over the Sea of Fertility, as detected by the Apollo 16 particle spectrometer, may indicate very recent volcanic gas venting in that region.

14. Analysis of the laser altimetry profiles from Apollo 16 confirms the earlier observation of the off-set of the lunar center of mass (about 2 km towards the Earth and about 1 km eastward), and gives the mean lunar radius as 1737.8 km. 15. The role of meteorite impacts in creating ancient lunar landforms has been understimated. In addition, we now have the first, and largely unexpected, evidence that impact processes are capable of creating surfaces with many of the same characteristics as those created by volcanic processes.

16. The indigenous lunar fossil magnetism is lunar-wide, but it is not represented by a simple dipole field as is Earth's magnetism. The lunar magnetic field is contained in crustal rocks that have been subsequently broken and reoriented. 17. The lunar surface was used as an astronomical observatory on Apollo 16 for an instrument called a far UV camera/spectrometer. The data show a huge amount of dissociated oxygen in the outer portions of the Earth's atmosphere that may represent an important source of the atmosphere's free oxygen. 18. Appreciable heat flowing from the Moon's interior is typical over wider areas than was believed likely a year ago.

SKYLAB

INTRODUCTION

In previous statements to this Committee, the NASA has provided much background material on the development and manufacturing aspects of the Skylab Program. Since Skylab (figure 92) (see p. 378) is now approaching the operational phase, this statement briefly focuses on the accomplishments of the recent past and directs considerable attention to the planned accomplishments of the near future.

As the Committee knows, Skylab is a three mission program (figure 93) (see p. 378) consisting of one 28-day and two 56-day manned flights spanning an 8month period. One day prior to the launch of the first manned mission, the Skylab itself will be launched and placed in orbit to await the arrival of the first crew. The launch of Skylab, SL-1, followed the next day by the launch of the first manned mission, SL-2, in mid-May, constitutes in effect a dual launch and marks the start of Skylab flight operations. Through the summer and fall

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of last year, Skylab flight hardware (figure 94) for the SL-1/SL-2 mission was

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delivered to Kennedy Space Center (KSC). This delivery was contingent on the completion of exhaustive integration and systems testing prior to acceptance by NASA. Extensive use of altitude and thermal/vacuum chambers to simulate flight conditions was an important test requirement. Below this level of testing and even more basic was the qualification test program now virtually complete. Out of the many hundreds of items to be qualified for flight, only eight remain to be completed.

One test program of special significance should be mentioned. Last summer the Skylab Medical Experiment Altitude Test (SMEAT) (figure 95) (see p. 380), of 56-day duration, was conducted in an altitude chamber at the Johnson Space Center (JSC) in a simulated Orbital Workshop environment. This test was designed to obtain baseline medical data, to determine the physiological effect of the environment on the three crewmen, and to insure the operational readiness of the integrated medical experiment system. The atmospheric constituents, pressures, food, water, waste management facilities, and experiment hardware were similar to those which will be used during the Skylab mission. It was a highly successful test and all objectives were satisfied. Hardware problems uncovered have been corrected in the flight units.

Having arrived at KSC, the flight hardware has undergone intensive checkout at the module level (figure 96) (see p. 380), including docking tests to verify the critical interface between the Multiple Docking Adapter and the Command and Service Module. Stacking of the SL-1/SL-2 space vehicles (figure 97) (see p. 381) has proceeded a pace and end-to-end integrated systems tests of the orbital assembly have been completed.

All the activities to date support a mid-May launch. Major activities which remain to be accomplished on SL-1 prior to rollout to the launch pad include the stowage and servicing of consumables like food and water, and the final flight stowage of experiment and operational equipment which is scheduled for early March. The readiness and operational compatibility of the Space Training Data Network with Skylab will be checked later this month, to assure that the communication systems will have the capacity to provide for the high data rate the experiments will produce. The Payload Shroud Nosecone, which provides boost

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protection for the Airlock Module/Multiple Docking Adapter and Telescope Mount will be installed next month and rollout to Pad 39A is scheduled for April. Work remaining on SL-2, which was transferred to Pad 39B earlier this month, only involves the standard launch preparations for manned space flight. Launch pad operations have been minimized to the greatest possible extent. The overall philosophy has been to conduct all possible testing and servicing. within the protected environment of the Vehicle Assembly Building and move the space vehicles to the launch pad only when they are virtually ready for flight. However, the Flight Readiness Reviews and Countdown Demonstration Tests remain to be accomplished prior to launch.

This brief status report has stressed the comprehensive nature of the test program. The test pyramid, starting at the component qualification level and building up through the levels of subsystem and module testing, through acceptance reviews and checkouts, to the Countdown Demonstration, provides the confidence needed to launch and operate America's first space station.

By this time next year the Skylab flights will be history, and initial assessment of the practical benefits and value of a manned research facility in Earth orbit will be well underway. The Skylab Program is predominantly utilitarian in nature, putting the space vehicles and operating know-how developed by Apollo in the service of a wide range of scientific and technological disciplines. In most of these, the use of a space platform is essential to the advancement of knowledge beyond that already acquired independent of space flight. In others, the advancement of space flight itself is the main purpose.

The scientific investigations to be conducted on the Skylab mission (figure 98) (see p. 382) embrace almost every discipline that can take advantage of the unique properties of the orbital environment-the broad view of Earth and the biosphere, the availability of the entire electromagnetic spectrum for celestial observations, and the elimination of the effects of gravity.

About 270 (figure 99) (see p. 382) separate scientific and technological investigations have been identified and validated for applicability to the disciplines involved. These investigations are being pursued by some 600 Principal Investigators and co-investigators, of which more than 250 are foreign professionals. Over

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