SCIENTIFIC INVESTIGATIONS IN SPACE

tucky (18th and 19th Semiannual Reports.) Investigators found that the rodents, birds, and small primates tested at gravity levels above 1 g in the laboratory avoided gravity higher than that on earth. Since gravity ranging from 1 g on earth to weightlessness can be produced only briefly on the ground, the study of its longduration effects must be carried out in orbiting spacecraft. However, zero gravity can be produced for several minutes in sounding rockets.

Four sounding rocket flight experiments exposed white rats to gravities below and above the earth's for five minutes (19th Semiannual Report, p. 57.) The experiments-launched from Wallops Station, Va. December 5, 1967, June 24 and November 21, 1968, and May 15 of this year-marked the first in-flight use of a centrifuge for biological purposes. During the flights the rats were able to select their preferred gravity level in a centrifugally-generated gravity field.

The test animals were fully conditioned by laboratory simulation to the noise, acceleration, spin, and vibration of the rocket at launch before experiencing the weightlessness of flight. They survived the launch and carried out the experiment during the reduced gravity period. Three out of four located themselves close to the level of earth gravity at the end of the five-minute test period. More flights of this type were planned. The same rocket (an Aerobee 150A) and payload will be used, but there will be up to 20 rats in these more complex experiments.

Physical Biology

The effects of various physical stresses on ribonucleic and deoxyribonucleic acids-RNA and DNA-in animal bacterial and viral cells were being studied at Pennsylvania State University. (RNA and DNA, complex organic acids, play important roles in protein synthesis and in heredity.) The investigators found that heat caused a rupture of these molecules, which then affected the genetic code. They also discovered that hydrostatic pressure applied to cell components influenced certain temperature-sensitive enzymes-affecting the amount of protein synthesized and reducing DNA synthesis, especially when the cell was under pressure.

Researchers at the University of Maryland discovered that brain cell RNA was reduced in adult rats centrifuged at various speeds to increase the gravitational level and determine the influence on cellular RNA. The extent of RNA reduction depended on the level of the g force and exposure time. The RNA level of these animals eventually returned to normal. When young rats were similarly

SEMIANNUAL REPORT (JANUARY-JUNE 1969)

exposed, it took three times as long for the same reduction of RNA.

Research at the University of California showed that DNA can exist in various forms, which are controlled by salt and relative humidity. Also, experiments with temperature-sensitive mutant viruses showed that short fragments of DNA, synthesized at increased temperature, became joined when temperature was decreased. A special enzyme (DNA ligase) was found to cause this joining.

LIGHT And MEDIUM LAUNCH VEHICLES

NASA used Scout, Delta, Agena, and Atlas-Centaur launch vehicles for its unmanned space missions.

Scout

The Agency was preparing a Scout vehicle to launch the Italian San Marco C spacecraft from the East Coast of Africa late this year or early in 1970. And, as requested by the European Space Research Organization (ESRO), NASA was arranging a Scout launching of the ESRO 1B spacecraft on a reimbursable basis during the latter part of 1969.

In addition, a contract to develop an improved Scout first stage motor was negotiated in June. This motor will perform 30 percent better without an appreciable increase in production unit cost.

Delta

Delta launched OSO-V on January 22, and the Canadian-American satellite ISIS-I January 30. This vehicle also orbited a fourth Intelsat II on February 5, and later that month the meteorological satellite ESSA IX. On May 21 it placed the third Intelsat III spacecraft in orbit. Two more satellites were launched in June by the Delta vehicle-Explorer XLI (IMP G) and Biosatellite III.

Agena

Nimbus III (April 14) and OGO-VI (June 5) were launched by Thorad-Agena vehicles. Also, preparations were underway to launch the Space Electric Rocket Test II this fall and Nimbus D in 1970. (The Nimbus D spacecraft is the last approved mission currently scheduled for a NASA Agena.)

Atlas-Centaur

In February and March, Atlas-Centaur vehicles injected the two Mariner Mars 1969 planetary spacecraft into Mars transfer orbits. The next Atlas-Centaur flight will be the launching of an Applications Technology Satellite (ATS-E) during the third quarter of the year.

As evidence of the skill of designers, builders, and launchers of highly complex spacecraft, Nimbus III (replacing Nimbus B destroyed at launch) was orbited in less than 11 months from the time NASA approved its mission. Further proof of this competence was the orbiting of sophisticated satellites of the ESSA and INTELSAT class.

METEOROLOGICAL SATELLITES

ESSA and TIROS

ESSA-IX (TOS-G) was launched by NASA for the Environmental Science Services Administration, ESSA, on February 26 (fig. 3-1.) Its Advanced Vidicon Camera System, AVCS, was providing global cloud pictures to ESSA ground stations at Gilmore Creek, Alaska and Wallops Island, Va. ESSA satellites II, V, VI, VII, and VIII also continued supplying global cloud-cover data through either their Automatic Picture Transmission (APT) or AVCS Systems. TOS-H was in storage and ready to be launched when needed by the National Operational Meteorological Satellite System.

Flight subsystems of TIROS-M were installed in the spacecraft and checked out (20th Semiannual Report, p. 79.) Integration and prequalification testing phases of this research and development satellite were almost completed. TIROS-M-scheduled for an October launch-will be the flight prototype for a second series of improved spacecraft of the TIROS Operational Satellite (TOS) class. Five operational spacecraft of this class were being procured to meet ESSA's needs during 1969-71.

Synchronous Meteorological Satellite

To satisfy ESSA requirements for continuous observation of the earth's atmosphere on an operational basis in the near future,

SPACE APPLICATIONS

initial research and development studies for a geostationary meteorological satellite system were underway. The system, using the Synchronous Meteorological Satellite (SMS), will be managed and operated by ESSA as part of the National Operational Meteorological System. Two operational prototype spacecraft, SMS-A and -B, were planned for development and flight test. Design of the SMS will be based on flight-proven hardware developed either in NASA's research and development program or in similar programs of other Government agencies. It allows day and night viewing.

Nimbus

Nimbus II was launched on May 15, 1966 and operated for 32 months-far beyond its designed lifetime (19th and 20th Semiannual Reports.) Nimbus III was placed into a near polar orbit, 676 to 703 miles above the earth, on April 14 of this year (fig. 3–2). An Army geodetic satellite, SECOR (Sequential Collation of Range), carried as a secondary payload on the Agena launch vehicle, was injected into a separate 690-mile circular orbit about 48 minutes after the Nimbus spacecraft separated from Agena. Nimbus and SECOR were operating as planned (fig. 3-3 and 3-4).

Image Dissector Camera System (IDCS) - Supplies daylight cloud cover

The vertical temperature profiles of the atmosphere derived from infrared radiation data measured by the IRIS and SIRS sounding experiments helped to advance meteorology. The temperature data obtained compared favorably with those supplied by local radiosondes. The MRIR provided invaluable information on worldwide distribution of water vapor, carbon dioxide, and strato