Development of a Small Satellite Series ISRO Experience

The development of a small Stretched Rohini Satellite Series (SROSS) in the Indian Space Research Organization (ISRO) has moved hand in hand with that of one class of indigenous launch vehicles, the Augmented Satellite Launch Vehicle (ASLV). In other words, these satellites have been developed as compatible payloads for those launch vehicles. The first two satellites SROSS-1 and SROSS-2 although were very versatile satellites carrying space science related payloads could not be orbited owing to failure of launch vehicles. The third satellite in the series, SROSS-C, was a smaller satellite launched by the third developmental flight ASLV-D3 on May 20, 1992. Earlier, the 40kg class rohini satellites (RS) were developed as payloads for the smaller launch vehicles (SLV-3) during the pre-eighties, which were suitably augmented to the Augmented Satellite Launch Vehicles to carry the 150 kg class Stretched Rohini Satellite Series during the pre and post nineties. This new satellite series were configured on the basis of a common bus concept, which are extremely compact, cost effective as well as innovative. It is compact because subsystems are very densely packed, cost effective because the bus is common and hence easily reproducible, and innovative because it is modular and hence easily reconfigurable. The paper describes some of these important aspects giving full narration of the development including pre-launch, launch and on-orbit operations of SROSS-C in detail

Science and technology of imaging from space

Imaging techniques from space, started mainly as a military reconnaissance tool, have come a long way from its early concepts to meet the present day needs of providing a precise metrology of the Earth processes and its features. The first part of the paper deals with the basic concepts of imaging from space. In this, the energy source available and the effect of atmosphere on the radiation are elaborated. Also the signatures of objects for identification and their characteristics in spatial and spectral domain are briefly touched upon. The second part of the paper deals with the challenges in realizing a satellite with limited volume and weight constraints by giving examples of very innovative approaches in the design of the optical systems for telescopes. The challenges associated with high resolution imaging and resulting high amount of data handling through appropriate data compression techniques are highlighted. The work presented here has been primarily carried out at the Indian Space Research Organization (ISRO). The paper concludes with an assessment of the futuristic direction that include improved algorithms for parameter retrieval and improved classification accuracies, improved models for atmospheric correction, new approach in artificial intelligence and expert systems for feature based classification, improved data compression techniques, ultra-light weight mirrors and adaptive optics, optical materials and detector arrays with built-in read out in the infrared region

Science and technology of imaging from space

Imaging techniques from space, started mainly as a military reconnaissance tool, have come a long way from its early concepts to meet the present day needs of providing a precise metrology of the Earth processes and its features. The first part of the paper deals with the basic concepts of imaging from space. In this, the energy source available and the effect of atmosphere on the radiation are elaborated. Also the signatures of objects for identification and their characteristics in spatial and spectral domain are briefly touched upon. The second part of the paper deals with the challenges in realizing a satellite with limited volume and weight constraints by giving examples of very innovative approaches in the design of the optical systems for telescopes. The challenges associated with high resolution imaging and resulting high amount of data handling through appropriate data compression techniques are highlighted. The work presented here has been primarily carried out at the Indian Space Research Organization (ISRO). The paper concludes with an assessment of the futuristic direction that include improved algorithms for parameter retrieval and improved classification accuracies, improved models for atmospheric correction, new approach in artificial intelligence and expert systems for feature based classification, improved data compression techniques, ultra-light weight mirrors and adaptive optics, optical materials and detector arrays with built-in read out in the infrared region

Dark and Dairy

notes: Extended version with footnotes available here: http://www.rajesh.io/street-metaphysics/?tag=Dharmapolispublication-status: PublishedCopyright © 2014 The HinduNewspaper - Opinio

SROSS C-2 detections of gamma ray bursts and the SGR 1627-41

The GRB monitor (GRBM) on board the Indian SROSS C-2 satellite has detected 53 classical gamma ray bursts since its launch in May, 1994 till its re-entry in July, 2001. For a subset of 26 events, locations were obtained from simultaneous observations by other gammaray detectors in space. The sky distribution of these 26 SROSS C-2 bursts is consistent with isotropy. The distribution of event durations shows evidence for bimodality. There is an evidence for a moderate hardness ratio-intensity (HIC) correlation in the data. The SROSS C-2 GRBM has also detected three episodes of emission from the SGR 1627-41

The design of space vehicles

In this paper, an attempt has been made to summarise the essential elements of a space vehicle design. After giving an overview of the methodology of spacecraft sizing and configuration, a brief outline of the technical considerations related to the design of different subsystems of the vehicle has been presented. The essential aspects related to manned systems are also discussed. The article concludes with the identification of some of the important payload interfaces, that are relevant to the design of material processing experiments in space

Search for optical bursts from the gamma ray burst source GBS 0526-66

Attempts were made to detect optical bursts from the gamma-ray burst source GBS 0526-66 during Dec. 31, 1984 to Jan. 2, 1985 and Feb. 23 to Feb. 24, 1985, using the one meter reflector of the Kavalur Observatory. Jan. 1, 1985 coincided with the zero phase of the predicted 164 day period of burst activity from the source (Rothschild and Lingenfelter, 1984). A new optical burst photon counting system with adjustable trigger threshold was used in parallel with a high speed photometer for the observations. The best time resolution was 1 ms and maximum count rate capability was 255,000 counts s(-1). Details of the instrumentation and observational results are presented

X-ray variability of GRS 1915+105 during the low-hard state observed with the Indian X-ray astronomy experiment (IXAE)

The galactic superluminal transient X-ray source GRS 1915+105 was observed with the pointed proportional counters (PPCs) onboard the Indian satellite IRS-P3 during 1996 July 23-27. We report here details of the behavior of this source during the relatively quiet and low luminosity state. Large intensity variations by a factor of 2 to 3, generally seen in black-hole candidates, are observed at a time scale of 100 ms to few seconds. No significant variation is detected over larger time scale of minute or more. The intensity variations are described as sum of shots in the light curve, and the number distribution of the shots are found to be exponential function of the fluence and duration of the shots. The cross correlation spectrum between 6-18 keV and 2-6 keV X-rays is found to have asymmetry signifying a delay of the hard X-rays by about 0.2 to 0.4 sec. This supports the idea of hard X-rays being generated by Compton up-scattering from high energy clouds near the source of soft X-rays. Very strong and narrow quasi periodic oscillations in the frequency range 0.62 to 0.82 Hz are observed. We discuss about a model which explains a gradual change in the QPO frequencies with corresponding changes in the mass accretion rate of the disk.Comment: 14 pages including 6 figures. To appear in Astronomy and Astrophysics Supplement Serie

Indian Space Programme

Modern space science had its beginnings around 1946 when scientists started the deployment of instruments to the outer fringes of the earth’s atmosphere using balloons and rockets to study radiations from outer space as well as geophysical phenomena. In spite of the professed scientific goals for the first earth satellite missions, the launch of SPUTNIK on 4 October 1957 by the then Soviet Union added a new dimension to the cold war between the US and the Soviet Union. The early scientific satellite missions of the US also had implicit goals of pursuing US interest in establishing the International legal principle that national sovereignty did not extend to the altitudes at which the satellite would orbit. Thus there was no obstacle in International law to the overflight of a reconnaissance satellite over Soviet territory. Against this backdrop, it is significant to note that the early inspiration for the Indian Space Programme came not from any military objectives, but from the interests of a large scientific community who have been actively engaged in research programmes related to geophysics and astrophysics

IXAE observations of the X-ray pulsar XTE J1946+274

We report results from two observations of the transient binary X-ray pulsar XTE J1946+274 with the Indian X-ray Astronomy Experiment (IXAE) made in September 18-30 1999 and June 28-July 7 2000. The pulsar has a ~80 days orbital period during which the X-ray intensity varies almost sinusoidally between intensity levels of 5 and 50 mCrab. The mid-time of the two observations with the IXAE are separated by an orbital phase of 0.56 and were in the decaying and rising parts of its orbital modulation, respectively. During both the observations, strong pulsations with 15.8 s period are detected in the 2-6 and 6-18 keV energy bands of IXAE. The pulse profiles in both the observations are double peaked and identical with a similar pulse fractions of ~30% in the two energy bands. The pulse periods and its local derivatives are obtained from the IXAE observations. The known pulse period history shows small deviations from an otherwise nearly constant spin-up trend of the pulsar since its discovery. If the measured local period derivatives are a sum of a nearly constant spin-up of the pulsar and effect of its orbital motion, it suggests that the orbit of this Be X-ray binary is eccentric. The RXTE-ASM light curve shows a continuous detection of 10 orbital modulation of the source since its discovery