We have performed a study on telecommunication systems for a hypothetical mission to Mars. The objective of the study was to evaluate and compare the benefits that microwave-X-band (8.4 GHz) and Ka-band (32 GHz) - and optical communications technologies a afford to future missions. The telecommunication systems were required to return data after launch and in orbit at 2.7 AU with daily data volumes of 0.1, 1.0, or 10.0 Gbits (Gb). Spacecraft terminals capable of delivering each of the three data volumes were proposed and characterized in terms of mass, power consumption, size, and cost. The estimated parameters for X-band, Ka-band, and optical frequencies are compared and presented here. For all cases, the optical light terminal exhibits about 60 percent of the mass of the corresponding radio frequency (RF) subsystem. Power consumption is comparable for all three technologies at a 0.1 Gb/day data volume, but the power required at either Ka-band or optical is less than half of the X-band requirement at 10 Gb/day. These benefits can be obtained only with a suitable investment in reception facilities for Ka-band or optical frequencies.

In this part-II of the advanced communications benefits study, tow critical metrics for comparing the benefits of utilizing X-band, Ka-band and Optical frequencies for supporting generic classes of Martian exploration missions have been evaluated. The first of these is the overall equivalent communications system mass on the spacecraft. The second comparison metric is the overall cost impact. This 'overall' cost assessment has considered the costs for both the spacecraft end of the link and the ground end. In both cases the metrics indicate that higher frequency communication bands have favorable mass and cost, particularly at higher data volumes transmitted daily to the earth. The same metrics are also applied to telecommunication for a hypothetical Neptune mission, extrapolating from the designs for the Mars case.

The LAser-Stabilized Imaging Interferometer (LASII) concept is being developed as an astronomical telescope for the next generation of optical resolution beyond Hubble Space Telescope (HST). The essential ingredients are: a rigid and stable structure to minimize mechanical and thermal distortion, active control of the optical geometry by a laser metrology system, a self-deploying structure fitting into a single launch vehicle, and ultraviolet operation. We have modified earlier design concepts to fit the scale of an intermediate sized NASA mission. Our present design calls for 24 0.5 m apertures in a Mills Cross configuration, supported on four trusses. A fifth truss perpendicular to the primary surface would support the secondary mirror and the laser metrology control points. Either separate interferometers or two guide telescopes would track guide stars. This instrument would have about 6 times the resolution of HST in the visible and the same collecting area. The resolution would reach 2.5 mas at 150 nm. The primary trusses would fold along the secondary truss for launch, and automatically deploy on orbit. Possible orbits are sun-synchronous at 900 km altitude, high earth orbit or solar orbit. Infrared capability could be included, if desired.

The induced-emission cross section of the copper laser lines $4p^{2}P_{\frac{3}{2}}\ensuremath{-}4S^{2}D_{\frac{5}{2}}$ (5106 \AA{}) and $4p^{2}P_{\frac{1}{2}}\ensuremath{-}4S^{2}D_{\frac{3}{2}}$ (5782 \AA{}) have been measured for He and Ne as buffer gases at different pressures by using an amplification-gain technique. The line broadenings are deduced from the experimental data and compared to the values predicted by a pressure-broadening impact theory.

The electron temperature as a function of laser tube temperature of a copper vapor laser utilizing copper chloride as a lasant has been obtained by measuring the microwave incoherent radiation from the plasma in the laser tube. An unexpected increase of electron temperature at higher laser tube temperature may be due mainly to Penning ionization of the Cu atom by the metastable state of He or Ne buffer gases. The results obtained in this work provide part of the basis for understanding the behavior of the laser output as a function of tube temperature.

A lead-vapor laser utilizing lead chloride as a lasant has been investigated. Lasing is attained by means of two consecutive electrical discharges. The maximum output is obtained at a vapor pressure of about 0.3 Torr at a temperature of 500°C, a time delay between electrical discharges of 150 μs, and an output mirror transmittance of 80%. The maximum energy density and power density are respectively 4 μJ cm−3 and 160 W cm−3.

A manganese vapor laser utilizing manganese chloride as a lasant has been observed and investigated. Lasing is attained by means of two consecutive electrical discharges. The maximum laser output is obtained at a vapor pressure of about 3 Torr, a temperature of 680°C, and a time delay between electrical discharges of 150 μsec. The maximum energy density is 1.3 μJ cm−3.

The result of the measurement of the electron-ion recombination rate of cesium plasma in a discharge tube is presented. The electron temperature has been extended to 5000 °K and the electron density to 1015 cm−3. The comparison of the experimental data with the calculated values (Ref. 7) is considered to be satisfactory

The pumping mechanism of a high-current pulsed CO2 laser has been investigated. It was found that there is a time delay of the laser pulse behind the current pulse. From the dependence of the time delay on the plasma parameters, such as electron density, electron temperature, gas temperature, gas pressure, and emission of oxygen atomic line (7771 Å), it can be shown that during the current pulse, the CO2 is totally dissociated into CO and O. The subsequent recombinations of CO and O into CO2 are responsible for the pumping of the upper level of the CO2 laser (10.6 and 9.4 μ). The time delay between the current pulse and laser pulse is thought to be due to the time required for CO and O to recombine to reach the threshold population for lasing for the particular optical cavity. The threshold upper level population is obtained by knowing the Q value of the optical cavity, wavelength of the laser line, and linewidth of the radiation line. By equating the amount of CO2 formed during the delay time to the threshold upper laser population, the reaction rate of CO+O→CO2 is thus obtained. The agreement between the rate obtained and previously determined supports the proposed pumping mechanism.

A giant pulse laser is focused in a gas flow by a lens. The plasma drop produced by the gas breakdown is used as a tracer for the flow velocity measurement. The motion of the plasma drop is detected by both electrostatic probe and drum-camera techniques. The estimated experimental error in the present setup is about 3%. The new features of this method are (1) very high spatial resolution, (2) minimum disturbance in the flow due to the instrumentation, and (3) applicability both to un-ionized and ionized flows.

A substantial lowering of the work function of a tungsten Langmuir probe immersed in an argon plasma in a discharge tube is observed. The mechanism is thought to be similar to the Schottky effect. The electron temperature measurement is lowered about 30%, in a particular discharge condition, as the probe goes from room temperature to 2000°C. The charge number density measurement, by saturation electron current appears to be higher by 15%, and that by ion saturation current appears to be higher by almost one order of magnitude. This phenomenon can also account for the discrepancy of the ratio of ion and electron saturation current obtained by previous authors and this author.

The nature of the flow of a dissociating diatomic gas in a convergent-divergent supersonic nozzle is investigated by measuring the distribution of flow parameters along the nozzle. Two parameters are measured, namely the degree of dissociation and the static pressure. The degree of dissociation is measured by a spectroscopic method. The pressure is measured by [xcup ]-tube manometers. The results are compared with Bray's (1959) theory and Logan's (1957) prediction.

A dark-field oscillatory spark microphotography technique has been developed to study with tracers the structure of the gas boundary layer in the shock tube. By using these particles as tracers, velocity profiles of the boundary layer both in laminar and turbulent regions are measured and the velocity fluctuations observed. The time and space resolution of this technique is high. Laminar velocity profiles show a significant deviation from theoretical expectations. The turbulent average velocity profiles have the usual 1/7th power variation with distance from the wall in the top 90% of the layer. The velocity of the flow within a few microns from the wall is sometimes much greater than the value predicted by Mirels assuming zero velocity at the wall. A possibility of slip flow in the shock tube is discussed. This technique allows measurements to be made as close to the wall as the size of the particle's diffraction pattern, which is about 1 μ.