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The Mars Surface Penetrator mission was designed to provide a capability for multiple and diverse subsurface science measurements at a low cost. Equipment required to adapt the Pioneer Venus spacecraft for the Mars mission is described showing minor modifications to hardware. Analysis and design topics which are similar and/or identical to the Pioneer Venus program are briefly discussed.
Data on the Jovian atmosphere and radiation environment transmitted by Pioneer 10 as it passed by Jupiter are discussed. The presence of a strong magnetic field, of energetic electron precursers, and of flat disk-shaped particle distribution is noted at a distance of 360 Jovian radii from the planet. Previously available data on Jovian satellites are augmented from Pioneer 10 data. The normal operation of the data collecting and transmitting systems of the mission after encounter with Jupiter is noted.
Pioneer 10 is the first earth-based vehicle to encounter Jupiter and occult its moon, Io. In contributing to the success of the mission, the Orbit Determination Group evaluated the effects of the dominant error sources on the spacecraft's computed orbit and devised an encounter strategy minimizing the effects of these error sources. The encounter results indicated that: (1) errors in the satellite model played a very important role in the accuracy of the computed orbit, (2) encounter strategy was sound, (3) all mission objectives were met, and (4) Jupiter-Saturn mission for Pioneer 11 is within the navigation capability.
Two spacecraft, Pioneers F and G, each with a launch weight of approximately 256 kg, were launched in March 1972 and April 1973 on trajectories which will result in close Jupiter encounters in late 1973 and 1974, respectively. The Pioneer mission objectives are to investigate the interplanetary medium beyond Mars, to determine the nature of the asteroid belt, and to explore Jupiter and its environment. A review is given of the system and subsystem design with emphasis on the simplicity of design, the selective use of redundancy for reliability enhancement, and the environmental protection provided.
In December 1973, Pioneer 10 became the first spacecraft to reach the vicinity of Jupiter. The spacecraft passed through the Jovian magnetosphere in two weeks and sent back more than 300 pictures of the big planet. Measurements were conducted of EM fields, energetic particles, and micrometeoroids. Radio occultations observed are discussed along with observations in the infrared and ultraviolet range, magnetic measurements, questions of trajectory analysis, and data obtained with the aid of a plasma analyzer. Pioneer 10 has confirmed as inescapable the fact that Jupiter radiates more energy than it receives from the sun.
Data obtained by the Pioneer 10 vector helium magnetometer are presented along with models of the intrinsic magnetic field of Jupiter and its magnetosphere. Data acquired between 2.84 and 6.0 Jupiter radii, where the intensity of the planetary field ranged between 1900 and 18,400 gamma, were used to develop a six-parameter eccentric dipole model of the field. The dipole so derived has a moment of 4.0 G (R sub J) cubed and a tilt angle with respect to Jupiter's rotation axis of 11 deg. A model of the Jovian magnetosphere is presented in which the essential feature is an eastward current sheet that forms an annulus with Jupiter at the center. At large distances from the planet the current sheet is nearly parallel to Jupiter's equator but, in general, does not lie in it. The current sheet is warped, so that it is above the equator on one side and below it on the other. The current sheet rotates with the planet, more or less like a rigid body, this behavior causes an apparent up and down motion and periodic crossings of the current sheet by Pioneer.
The results of background starlight observations are reviewed that were obtained by the Pioneer 10 asteroid-Jupiter probe when, after passage beyond the asteroid belt, its imaging photopolarimeter observed integrated starlight and diffuse galactic light for the first time in the absence of zodiacal light. Brightnesses in the blue are presented with and without individually resolved stars for regions of the sky observed when Pioneer 10 was 4.64 astronomical units from the sun.
The basic concept of designing a scientific entry probe for the expected range of environments at Saturn or Uranus and making the probe compatible with the interface constraints of the Pioneer spacecraft was investigated for launches in the early 1980's. It was found that the amount of hardware commonality between that used in the Pioneer Venus program and that for the Saturn/Uranus probe was approximately 85%. It is recommended that additional development studies be conducted to improve the hardware definitions of the probe design for the following: heat shield, battery, nose cap jettisoning, and thermal control insulation.
The Pioneer 10/11 spacecraft and scientific instruments are described. The Pioneer 10/11 trajectories are described, mission objectives are discussed, and a summary of scientific findings is presented. Results obtained during the traverse of the Asteroid Belt show that the particle concentration is less than had been expected and does not present an appreciable hazard to spacecraft passing through the Belt. The results from six scientific instruments that measured the particle and field phenomena within the Jupiter radiation belt present a consistent picture which, in general, is an environment more severe than normal previous predictions based on earth observations.
The Pioneer 6 to 9 interplanetary spacecraft were launched in 1965, 66, 67, and 68. All continue to operate in various orbits about the sun, gathering data on the solar system environment. Pioneer 10 was launched in 1972, and is now more than halfway to Jupiter, with all systems performing their required functions. The paper reviews these programs and the few anomalies which have been observed. The long-term mission success is discussed in terms of possible causative factors: simplicity in design and operation, redundancy in function and in equipment, comprehensive development and acceptance tests, the mildness of the space environment, and luck.
The longest two-way telecommunications link ever established connected Pioneer 10 with its controllers and experimenters on earth during the first Jovian encounter. This radio link, operating in the 2.1 and 2.3 gigahertz frequency bands, maintained high-quality communications over a distance of 5-1/2 astronomical units. The data collected by eleven on-board advanced scientific instruments were transmitted to the investigators, providing a new wealth of information about the largest planet of the solar system. A descriptive review is presented of the spacecraft design and the ground data system configuration with an analysis of the telecommunications downlink. Pioneer 10, aided by Jupiter's gravitational field, is the first spacecraft to leave the solar system. A plaque attached to the spacecraft represents man's first attempt to send a message to another intelligence within our galaxy.
On the basis of recently calculated models of the Jovian atmosphere, a value of 5.0 was derived for the H2/He mixing ratio from the Pioneer 10 infrared radiometer data. A far-infrared spectrum corresponding to the thermal profile obtained in the Pioneer S-band occultation experiment was also computed. The spectrum strongly suggests a misinterpretation of the data obtained in that experiment.
This paper discusses the Pioneer Jupiter Orbiter/Probe mission with emphasis on the orbiter spacecraft system. In this mission, the atmosphere of Jupiter will be investigated for physical and chemical structure by a probe which survives entry and transmits data while descending below the 10-bar level. The spacecraft deflects after probe separation to a nonimpacting approach trajectory, acts as a communications relay for data from the descending probe, and propulsively enters an orbit about Jupiter. As an orbiter, it explores the environment of Jupiter for three years, making in situ measurements of the particles and fields of the Jovian magnetosphere together with remote measurements (including images) of Jupiter and the Galilean satellites. The spacecraft system is logically based on the design of Pioneers 10 and 11 with modifications for these different mission requirements: antenna, receiver, and memory for the probe-spacecraft data link; a retropropulsion system for the high velocity-change requirements of orbit insertion; a data system consistent with the requirements of a line-scan imaging system; and an improved complement of radioisotope-thermoelectric-generator power sources to provide adequate power six years after launch.
This paper discusses measurements of the energetic-particle population inside Jupiter's magnetosphere as well as observations of energetic particles in interplanetary space that have escaped from that magnetosphere. The discussion is based on Pioneer 10 data obtained when the spacecraft was outside the bow shock but within about 1 AU of the planet and on electron data obtained near earth by various IMP spacecraft. Pioneer 10 particle measurements in the Jovian magnetosphere are reviewed, the differential proton and electron energy spectra are described, and it is suggested that very little particle acceleration occurs in the outer magnetosphere. Additional data are examined in regard to Jovian alpha particles, proton and electron angular distributions, protons in the inner magnetosphere, effects of Io on the proton flux, electron acceleration outside the bow shock, and observations of Jovian electrons near earth. All these data are shown to support the conclusion that most, if not all, quiet-time increases in low-energy electron fluxes near earth are of Jovian origin.
The current status of the Pioneer 10 and 11 missions and Pioneer Venus 1978 mission was described.
The salient features of the various models of Jupiter's magnetosphere are compared with each other and with the major findings of Pioneer 10 and 11. No single model explains all the major phenomena detected by the Pioneers. A unified model of Jupiter's magnetosphere is proposed.
Possible improvements in the Deep Space Network and their potential effect on the telecommunications limit of Pioneer 10 and on Pioneer 11 Saturn encounter are discussed.
Temperature profiles for low latitude regions of Jupiter in the 1.0-0.1 bar pressure regime are recovered from Pioneer 10 infrared radiometer data. The temperature near 0.1 bar is 108-117 K, depending on the overlying thermal structure assumed. For the South Equatorial Belt (SEB), the temperature at 1.0 bar is 170 K, assuming an adiabatic lapse rate in the deep atmosphere. The South Tropical Zone temperature at this level is 155 K if pure gaseous absorption is assumed. The temperature is much closer to that in the SEB, assuming the presence of an optically opaque cloud near the 0.6 atm (145 K) level. Such a cloud presence in the STrZ may be correlated with the visible and 5 micron appearance of the planet and with NH3 saturation just below this position. The molar fraction of H2 most consistent with the data is 0.91 + or - 0.08. The effective temperatures of the SEB and STrZ are 127.6 and 124.2 K, respectively. A discrepancy with the preliminary neutral atmosphere inversion of Pioneer 10 radio occultation data remains unexplained.