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Description of instrumentation on the explorer xii satellite to digitize, store and read out the data obtained from cosmic ray detection equipment
Most of the understanding of the thermosphere resulted from the analysis of data accrued through the Atmosphere Explorer satellites, the Dynamics Explorer 2 satellite, and observations from rockets, balloons, and ground based instruments. However, new questions were posed by the data that have not yet been answered. The mesosphere and lower thermosphere have been less thoroughly studied because of the difficulty of accessibility on a global scale, and many rather fundamental characteristics of these regions are not well understood. A wide variety of measurement platforms can be used to implement various parts of a measurement strategy, but the major thrusts of the International Solar Terrestrial Physics Program would require Explorer-class missions. A remote sensing mission to explore the mesosphere and lower thermosphere and one and two Explorer-type spacecraft to enable a mission into the thermosphere itself would provide the essential components of a productive program of exploration of this important region of the upper atomsphere. Theoretical mission options are explored.
Upper atmosphere neutral atomic H and He composition, measuring number density variations with height and latitude from Explorer 32 satellite
The results are presented of the mission analysis performed by Computer Sciences Corporation (CSC) in support of the International Ultraviolet Explorer (IUE) satellite. The launch window is open for three separate periods (for a total time of 7 months) during the year extending from July 20, 1977, to July 20, 1978. The synchronous orbit shadow constraint limits the launch window to approximately 88 minutes per day. Apogee boost motor fuel was computed to be 455 pounds (206 kilograms) and on-station weight was 931 pounds (422 kilograms). The target orbit is elliptical synchronous, with eccentricity 0.272 and 24 hour period.
Ionospheric electron temperature and density by cylindrical electrostatic probes aboard Explorer 31 and Alouette 2 satellites
The ultraviolet nitric oxide spectrometer (UVNO) experiment on the Atmosphere Explorer D (AE-D) satellite measured thermospheric nitric oxide during the winter of 1974-1975 using resonant fluorescence from the 1-0 gamma band of the molecule. Almost complete latitude coverage was obtained, but the observations were confined to morning local times close to 0900. The 1-0 gamma band intensity profiles measured by the instrument were inverted to provide vertical profiles of the NO number density between about 90 and 200 km. Typically, the measured NO concentrations reached a maximum between altitudes of 100 and 110 km, and more NO was observed at higher latitudes than at low latitudes, in agreement with previous observational studies. The shape of the NO profile was also found to be a function of latitude, with a plateau appearing in the profile near 130 km for low latitudes and mid-latitudes in the winter hemisphere.
Energetic Particle Explorer satellite probe of particles in Van Allen radiation belt
Neutral particle and electron density measurements by Explorer 32 proving thermospheric gravity waves association with wave-like structure in F region electron density
Results are presented for calculated and observed incoherent scatter radar data on ionospheric and atmospheric properties during the crossings of the Atmospheric Explorer-C satellite over the Millstone Hill, Massachusetts incoherent scatter radar station. The incoherent scatter radar measured electron density vertical profiles and electron and ion temperatures. These values yielded the exospheric temperature and the vertical distribution of neutral gas temperature. The satellite measured electron and ion temperatures and densities, neutral gas composition, and photoelectron spectra. Measurements were also made of solar UV and EUV fluxes, the vertical profile of the NO number density, and the vertical profile of the 6300 A airglow-volume emission rate. The results are compared to those of a time-dependent coupled model of the ionospheric E- and F-regions. Good agreement is found between satellite results, incoherent scatter radar measurements, and model calculations. Along the orbital path satellite measurements show significant latitudinal gradients in the measured properties.
For a number of years, satellites have been employed to measure auroral particles and fields within the high-latitude thermosphere. In the present paper, data from orbit 1174 of the Dynamics Explorer 2 satellite on October 21, 1981, are utilized to calculate the structure of the ionosphere and thermosphere below the satellite altitude down to about 80 km. Attention is given to details regarding the DE 2 measurements, a satellite track model, the calculated ionospheric structure, and the calculated neutral gas heating rates. The investigation demonstrates that the technique of deriving characteristics of the ionosphere and atmosphere below a satellite track promises to be very fruitful for defining the characteristics of the lower thermosphere for use in large numerical models of the thermosphere and ionosphere.
Cylindrical electrostatic probe measurements on Alouette 2 and Explorer 31, considering implications for future missions
The calibration technique, which contains the calibrated backscattered radiance values necessary for performing the calibrations, is presented. The calibration constants for September to October 1981 to determine total columnar ozone from the Spin-Scan Ozone Imager (SOI), which is a part of the auroral imaging instrumentation aboard the Dynamics Explorer 1 Satellite, are provided. The precision of the SOI-derived total columnar ozone is estimated to be better than 2.4 percent. Linear regression analysis was used to calculate correlation coefficients between total columnar ozone obtained from Dobson ground stations and SOI which indicate that the SOI total columnar ozone determination is equally accurate for clear or cloudy weather conditions.
A review is made of ionospheric data reported since the IGY from rocket and satellite-borne ionospheric experiments. These include rocket results on electron density (RF impedance probe), D-region conductivity (Gerdien condenser), and electron temperature (Langmuir probe). Also included are data in the 1000 kilometer region on ion concentration (ion current monitor) and electron temperature from the Explorer VIII Satellite (1960 xi). The review includes suggestions for second generation experiments and combinations thereof particularly suited for small sounding rockets.
It is pointed out that thermospheric heating in the auroral zone and polar cap is of great importance to the variations in the high-latitude neutral wind and the resulting global temperature and densities. The considered investigation is concerned with relating in a quantitative manner the energy inputs from the Joule heating and particle inputs with the thermospheric responses, taking into account the cusp region, and the region of the eastward auroral electrojet. The data used in the investigation were obtained by the Atmosphere Explorer C satellite in late December 1974. Attention is given to electric fields derived from ion drift measurements, electric field strength and particle energy flux measured by the low energy electron experiment for AE-C orbit 4708, electron density contours, Joule heating contours, and height integrated Joule heating and particle energy flux.
Atmospheric optical emission measurements by the Visible Airglow Experiment (VAE) on board the Atmosphere Explorer (AE-C, D and E) satellites have been analyzed and found to be contaminated at low altitudes. The contamination maximizes in the forward direction along the spacecraft velocity and is sensitive to the composition and density of the ambient atmosphere. Analysis at two different wavelengths suggests that the contamination is likely to have a diffuse band spectrum which is brighter toward the red. Some unknown processes which involve satellite surface materials and the incoming ambient particles are believed to be responsible for the contamination. A simulation model is presented here to account for the observed angular dependence.
A Modular Antenna Pointing System (MAPS) is described which was designed for on-orbit servicing and on-orbit exchange. The MAPS provides a data link between the Explorer Platform (EP) satellite and the Tracking and Data Relay Satellite (TDRS). The MAPS consists of a two axis gimbal set used fo position a High Gain Antenna (HGA) toward TDRS, system control electronics, and an extendable mast. The system was qualified and integrated with the EP satellite for an April 1992 launch.
This paper gives a comprehensive summary of cosmic-ray intensity observations at high latitudes over North America and over Australia in the altitude range 550 to 1100 kilometers by means of Geiger tubes in Explorer VII (Earth satellite 1959 Iota). The time period covered is October 13, 1959 to February 17, 1961. Of special interest are the observational data on some 20 solar cosmic-ray events including major events of early April 1960, early September 1960, and of mid-November 1960. Detailed study of the latitude dependence of solar cosmic ray intensity will be presented in a later companion paper.
Orbital parameters and working characteristics of geodetic Explorer satellites