Telemetry,telecommand and safety sub-systems for scientific ballooning from Hyderabad

Highly sophisticated balloon-borne scientific payloads have stringent requirement on the telemetry and command system. The development and fabrication of the on-board TT&C package for telemetry, tracking, command, safety and ranging for these experiments is done in-house at the National Balloon Facility (NBF) at Hyderabad. In the last few years, we have made major improvements both in the ground station and the on-board sub-systems, thereby improving the data quality, data handling speed and the general flight control along with aviation safety. The new system has telemetry data rate up to 1 Mbps. A reduction in weight, power and cost of the reengineered on-board integrated package has also lead to the ease of operation during field tests prior to launch and at remote recovery sites. In this paper, we describe the details of the new control package, its flight performance and our plans for portable S-band telemetry and telecommand system to cater to the balloon flights from Antarctic station and long duration balloon flights.     

Evolution of scientific ballooning and its impact on astrophysics research

As we celebrate the centennial year of the discovery of cosmic rays on a manned balloon, it seems appropriate to reflect on the evolution of ballooning and its scientific impact. Balloons have been used for scientific research since they were invented in France more than 200 years ago. Ballooning was revolutionized in 1950 with the introduction of the so-called natural shape balloon with integral load tapes. This basic design has been used with more or less continuously improved materials for scientific balloon flights for more than a half century, including long-duration balloon (LDB) flights around Antarctica for the past two decades. The U.S. National Aeronautics and Space Administration (NASA) is currently developing the next generation super-pressure balloon that would enable extended duration missions above 99.5% of the Earth’s atmosphere at any latitude. The Astro2010 Decadal Survey report supports super-pressure balloon development and the giant step forward it offers with ultra-long-duration balloon (ULDB) flights at constant altitudes for about 100 days.     

The theoretical advantages and practical considerations of gas replenishment techniques in long-duration scientific ballooning

Long-duration scientific balloon flights using conventional ballasting methods to compensate for daily loss of lift suffer a severe payload weight penalty. Typically, the weight of the expendable ballast approaches or exceeds the weight of the balloon and payload. This paper examines the concept of correcting for degraded lift by “gas replenishment” techniques, that is, by replacing lost helium inflatant from an on-board dewar. Appropriate equations are developed and curves are presented which demonstrate the clear theoretical superiority of the replenishment method. Design problems associated with the dewars and heat exchangers required to implement the gas replenishment concept are also discussed in detail. A series of curves is presented in which net load, dewar weight and quantity of helium required are plotted for specific balloons and float altitudes as a function of daily loss rate. The lack of relevant heat exchange data in the literature is cited as an obstacle to immediate prototype development.     

Present status and new trends in scientific ballooning in India

The efforts in scientific ballooning in India have always been focussed towards continuous upgrading of capabilities in all aspects of balloon flights - balloon material, balloon fabrication, launch techniques, heavy payload launch, telemetry, telecommand and other ground facilities - to meet the growing demands of the scientific community. A brief account of recent progress in several of these aspects and future plans for further improvements in scientific ballooning capability is presented.     

The magnetosphere as a complex system

The magnetosphere is a complex system, with multi-scale spatio-temporal behavior. Self-organization is a possible solution to two seemingly contradicting observations: (a) the repeatable and coherent substorm phenomena, and, (b) the underlying self-similar turbulent behavior in the plasma sheet. Such states, are seen to emerge naturally in a plasma physics model with sporadic dissipation, through spatio-temporal chaos.     

The response of the Hermean magnetosphere to the interplanetary magnetic field

The interaction between the solar wind and Mercury is anticipated to be unique because of Mercury’s relatively weak intrinsic magnetic field and tenuous neutral exosphere. In this paper the role of the IMF in determining the structure of the Hermean magnetosphere is studied using a new self-consistent three-dimensional quasi-neutral hybrid model. A comparison between a pure northward and southward IMF shows that the general morphology of the magnetic field, the position and shape of the bow shock and the magnetopause as well as the density and velocity of the solar wind in the magnetosheath and in the magnetosphere are quite similar in these two IMF situations. A Parker spiral IMF case, instead, produces a magnetosphere with a substantial north–south asymmetric plasma and magnetic field configuration. In general, this study illustrates quantitatively the role of IMF when the solar wind interacts with a weakly magnetised planetary body.     

Antiparticle content in the magnetosphere

In the present work we assess the stable and transient antiparticle content of planetary magnetospheres, and subsequently we consider their capture and application to high delta-v space propulsion. We estimate the total antiparticle mass contained within the Earth’s magnetosphere to assess the expediency of such usage. Using Earth’s magnetic field region as an example, we have considered the various source mechanisms that are applicable to a planetary magnetosphere, the confinement duration versus transport processes, and the antiparticle loss mechanisms. We have estimated the content of the trapped population of antiparticles magnetically confined following production in the exosphere due to nuclear interactions between high energy cosmic rays (CR) and constituents of the residual planetary upper atmosphere.The galactic antiprotons that directly penetrate into the Earth’s magnetosphere are themselves secondary by its nature, i.e. produced in nuclear reactions of the cosmic rays passing through the interstellar matter. These antiproton fluxes are modified, dependent on energy, when penetrating into the heliosphere and subsequently into planetary magnetospheres. During its lifetime in the Galaxy, CR pass through the small grammage of the interstellar matter where they produce secondary antiprotons. In contrast to this, antiprotons generated by the same CR in magnetosphere are locally produced at a path length of several tens g/cm² of matter in the ambient planetary upper atmosphere. Due to the latter process, the resulting magnetically confined fluxes significantly exceed the fluxes of the galactic antiprotons in the Earth’s vicinity by up to two orders of magnitude at some energies.The radiation belt antiparticles can possibly be extracted with an electromagnetic-based “scoop” device. The antiparticles could be concentrated by and then stored within the superimposed magnetic field structure of such a device. In future developments, it is anticipated that the energy of the captured antiparticles (both rest energy and kinetic energy) can be adapted for use as a fuel for propelling spacecraft to high velocities for remote solar system missions.     

The accuracy of present models of the high altitude polar magnetosphere

The Polar satellite has explored the high-latitude, high-latitude magnetosphere out to 9 Earth radii (Re). The magnetic field data returned from this mission can be used both to provide data for new empirical models and to test existing models. Tests include comparing the observed location of the polar cusp with its position in the empirical models and comparing the strength of the magnetic field in the surrounding region. Near the cusp the magnetosphere is quite sensitive to solar wind conditions. In particular the energy density of the cusp plasma depends on the pressure of the solar wind applied to the interface of the cusp and the sheath. The applied pressure in turn depends on the shape of the magnetopause and the orientation of that interface, both controlled by the direction of the interplanetary magnetic field. Magnetohydrodynamic (MHD) models provide a coarse picture of the magnetosphere at high latitudes. While generally quite realistic, these too require testing against observations because even the MHD models must make some simplifying assumptions.     

Power line radiation in the magnetosphere

VLF radiation from electrical power transmission lines stimulates nonlinear wave-particle and wave-wave interactions in the magnetosphere, resulting in wave growth, triggering of emissions, and entrainment of other natural or manmade VLF waves. Examples of these effects will be reviewed using both ground-based and satellite data. In many instances, the interpretation of data is aided by Siple transmitter results that show similar spectral characteristics.     

Probing the magnetosphere with artificial electron beams

Since 1970 the Minnesota group has completed five sounding rocket experiments in which electron beams were injected into the magnetosphere at ionospheric heights and the interaction of the beams with the nearby and distant magnetosphere studied. By the technique of precisely locating conjugate region beam echoes the distant electric and magnetic field structures were studied by mapping into the local ionosphere. Ionospheric fields were measured directly for comparison. Subjects studied included gradient and curvature drifts, electric field drifts, electron pitch angle diffusion and other types of interactions with the tail plasma sheet region and the nearby ionosphere and atmosphere. The beams were also studied by plasma wave and ground-based electromagnetic detectors, by ground-based low light level television techniques and by extensive on-board rocket x-ray, photometer and particle detectors. Vehicle potentials and neutralizing processes and beam-ionosphere interactions have also been studied but will not be discussed in this paper.     

On the negligible role of manned missions for the geological exploration of Mars: a commentary.

At the 28th Plenary Meeting of the Committee on Space Research (COSPAR) in The Hague, The Netherlands, there was on June 28, 1990, a session of commission MF.1 on Impact of Human Expeditions to Mars, in which, among others, the benefits of manned Mars missions for the geological survey of Mars were discussed. The present commentary does not intend to discuss the pros and cons of manned space flight or of Mars exploration at large, but will reiterate some of the points made in that discussion concerning the justification of manned versus automated Mars exploration in the context of geologic sciences.     

The magnetopause erosion and the magnetosheath magnetic field penetration into the dayside magnetosphere

The earthward displacement of the magnetopause observed during a southward IMF (or the magnetopause erosion) and its dependence on the solar wind plasma and magnetic field parameters is studied by investigating data of about 30 magnetopause crossings by the ISEE 1 and 2 spacecraft. It is shown that the magnetopause erosion may be explained by a depression of the magnetic field intensity in the dayside magnetosphere caused by the penetration of the magnetosheath magnetic field (component perpendicular to the reconnection line) into the magnetosphere. The penetration coefficient (the ratio of the intensity of the penetrated field to the intensity of the magnetosheath magnetic field) is estimated and found to equal approximately 1.     

The role of image processing in mineral exploration: Why stop at Landsat?

Digital image processing procedures can be applied to data other than Landsat. Registered images of ancillary data such as may be derived from airborne magnetic and radiometric surveys provide new insights into existing data and extend the usefulness of satellite imagery. In times of increasing costs and difficulty of exploration better information handling is at a premium. It should be remembered that the field geologist is the ultimate end-user of most geological information, and as such the data should be easily useable and interpretable by him.