Using the albedo neutron decay source, the energy spectrum of trapped protons in the inner belt has been calculated from 10 to 700 Mev. This calculation differs from those of Singer and Hess in that a nuclear interaction term, in addition to the energy loss term, has been used in the continuity equation for the steady‐state condition. The spectrum agrees well with the published data. This agreement is strong evidence for the albedo neutron decay source. It also indicates that nonadiabatic losses are small for the particles measured here. A second small stack of nuclear emulsions was flown at the lower edge of the inner radiation belt 11 days after the large solar flare of May 10, 1959. The ratio of the proton flux measured on the second flight to that on the first one is 0.8±0.1, indicating that the solar flare had little or no effect on the proton content of the inner belt. A flux of 2±1 tritons/cm2 sec between 126 and 200 Mev was observed; it is attributed to collisions of trapped protons with air nuclei. No other nuclei heavier than protons were seen.

A nuclear emulsion stack was flown on an Atlas vehicle on October 13, 1960. The vehicle was launched from Cape Canaveral, went to a maximum altitude of 1185 km, and was recovered near Ascension Island. Protons with energies above 17 Mev were measured. The number of protons/(cm•)(sec)(Mev) between 1000 and 1185 km is 0.6 __.0.1 of the value obtained on the previous flight of April 7, 1959, between the altitudes of 1000 and 1230 km. The energy distribution is in excellent agreement with that measured on the April 7 flight. The maximum in the energy distribution at 75 Mev that was observed by the Los Alamos group on a flight in July 1959 is no longer visible. At 30 Mev the energy distribution departs from the theoretical distribution which is calculated using the cosmic-ray albedo neutron decay source and ionization and nuclear collision loss mechanisms. This deviation is probably due to a minimum in the albedo neutron energy distribution caused by a large neutron nonelastic cross section in nitrogen and oxygen at about 20 Mev. If this explanation is correct, the proton energy distribution should rise rapidly below 10 Mev to meet the theoretical curve. The experimental data also fall below the theoretical curve at energies above 300 Mev. This deviation may be caused by additional loss mechanisms that preferentially affect the high-energy protons, such as the breakdown of the adiabatic condition or the presence of hydromagnetic waves. It may also be due to a trapping probability that decreases with increasing energy or to a neutron energy distribution that drops off more rapidly with energy than the E -•' used in the calculation. The albedo neutron energy spectrum is derived assuming it is the only source of the trapped protons and the only loss mechanisms are ionization and nuclear coli•ions. Phys. Rev., 76, 914, 1949. Camerini, Lock, and Perkins, Progress in cosmic ray physics, edited by J. G. Wilson, North ]•olland Publishing Co., Amsterdam, 1, 24, 1957. Dragt, Effect of hydromagnetic waves on the lifetime of Van Allen radiation protons, J. Geophys. Research, 66, 1641, 1961. Freden and White, Protons in the earth's magnetic field, Phys. Rev. Letters, 3, 9, 1959. Freden and White, Particle fluxes in the inner radiation belt, J. Geophys. Research, 65, 1377, 1960. Hess, Van Allen belt protons from cosmic-ray neutron leakage, Phys. Rev. Letters, 3, 11, 1959. Hess, Patterson, Wallace, and Chupp, Cosmic-ray neutron energy spectrum, Phys. Rev., 116, 445, 1959. COSMIC-RAY ALBEDO NEUTRON FLUXES 29

Measurements were made of electron fluxes and spectrums above 900 kev at altitudes between 200 and 700 km in early September and October 1962 aboard two near‐polar Air Force satellites. The particle fluxes were observed with shielded solid‐state detectors having a 2π solid angle. The results show that electrons are lost from the radiation belts into the atmosphere along narrow ranges of L near L = 1.2 and L = 2 as well as in the L = 3 to 8 region. The L = 2 and L = 3 to 8 fluxes and spectrums exhibit temporal variations. A typical precipitating flux at B = 0.35 gauss, L = 2.0, is 103/cm2 sec with E > 0.9 Mev. A typical integral energy spectrum for L = 2, B = 0.35 gauss, is E−3 between 0.9 and 1.7 Mev. Comparison of results with pre‐Starfish measurements indicates that the fluxes of electrons observed near L = 1.2 and L = 2 are not connected with the high‐altitude explosion of July 9, 1962.

Three similar horizontal solar cells were deployed by the Apollo 11 astronauts to measure whether the lunar module ascent caused degradation of their surface properties and resultant thermal control. The outputs of the cells at lunar module ascent decreased approximately 18%, 7%, and 0%. The average absorptivity thus decreased approximately 8%, while the average emissivity decreased approximately 12%, resulting in overheating. The results are discussed and several possible causes are suggested. Subsequently, the surface absorptivity and emissivity of each cell changed less than 1%–2% during the following month. Lunar module ascent effects for the closely deployed Apollo 11 instruments were therefore much more important than the long-term exposure to the lunar environment. The relevance of these findings to future deployment of lunar instruments is discussed.

The omnidirectional differential spectrum of trapped protons was measured in the energy range from 10 to 200 Mev in August 1964. At L <˜ 1.3 and B ≈ 0.20 the measurements yield a spectrum that is the same as that measured in 1960 by Freden and White. At L values above about 1.4 there is a sharp increase in the proton flux below ≈35 Mev compared with the spectrum for L <˜ 1.4. The differential spectrum for Ep <˜ 35 Mev at L >˜ 1.4 can be represented by a power law of the form E−n, where E is the proton energy. The exponent n is found to be a function of B and L. For example, at L = 1.6, B/B0 = 1.0, n = 3.75; and at B/B0 = 3.0, n = 2.3. At L = 2, B/B0 = 3.0, n = 4.2, and at B/B0 = 6.0, n = 3.4. The spectrum of protons above 55 Mev does not show the same B, L dependence. These data are evidence that at least two important sources of trapped protons exist in the same region of space.