What is Astrosat

India: Astrosat and AIS-Sats launched on PSLV-C30

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September 29, 2015, 2:35 p.m.

On September 28, 2015, a PSLV launcher launched the Indian Astrosat space observatory and 6 satellites for monitoring ship traffic from ramp number 1 of the Satish Dhawan space flight center of the Indian Space Research Organization (ISRO) on the island of Sriharikota on India's south coast.

PSLV-C30 took off
(Image: ISRO)
The first stage of the rocket with the mission-related designation PSLV-C30 was supported by six additional, side-mounted boosters, the rocket flew in the so-called XL version. The latter came with the launch of the Chandrayaan 1 lunar probe (PSLV-C11), the GSAT 12 communications satellite (PSLV-C17), the RISAT 1 radar satellite (PSLV-C19), the MOM alias Mangalyaan (PSLV-C25) and navigation satellites for the regional Indian satellite navigation system IRNSS in use.

The flight of the PSLV-C30 projectile, 44.4 meters high and weighing around 320.2 tons, with Astrosat at the tip, began at 10:00 a.m. local time (IST) and 6:30 a.m. CEST on September 28, 2015 End of a countdown lasting exactly 50 hours.

After using up the solid fuel in the side-mounted boosters of the type PS0M-XL and the first stage with the designation PS1, as well as the ignition of the second, with the liquid fuels UH25 (75% asymmetrical dimethylhydrazine (UDMH) + 25% hydrazine hydrate) and N2O4 (Nitrous tetroxide) powered rocket stage PS2, the payload fairing was thrown off.

Then the third stage PS3 went into action, burning solid fuel. In the fourth and final PS4 rocket stage, liquid propellants were used again, here MMH as fuel and a mixture of nitrogen oxides (MON-3) as oxidizer. After the PS4 had done its job, after a short 37-second free flight phase, 32 minutes and 22.92 seconds after take-off, the astronomy satellite with a launch mass of 1,513 kilograms (unfueled 1,470 kilograms) was disconnected.

PSLV-C30 has cleared the tower
(Image: ISRO)
After the launch of Astrosat, an automatic, preprogrammed sequence ran on board the IRS-1-based satellite with a base body measuring 1.96 x 1.75 x 1.3 meters, at the end of which the two solar cell booms were successfully deployed .

The start of use of the two solar cell booms, which together provide a maximum of around 2,100 watts of electrical power, was able to be started by the tracking network called ISRO Telemetry, Tracking and Command Network alias ISTRAC with its center and mission operations complex (MOX) in Bangalore, India, which now monitors and monitors the satellite controls, confirm on the basis of received telemetry data.

Storage of electrical energy on board Astrosat is made possible by two lithium-ion battery sets with a capacity of 36 ampere hours each.

Milestones of the PSLV-C30 flight
(Image: ISRO)
According to ISRO, the planned orbit was reached with great accuracy. Astrosat entered an earth orbit with a perigee, the orbit closest to the earth, of approximately 644.6 kilometers, and an apogee, the orbit furthest from the earth, of approximately 651.5 kilometers. The inclination of the orbit towards the earth's equator is around 6 degrees. Direct contact between the Astrosat control center and the satellite is possible during 10 out of 14 earth orbits per day.

In the coming days, ISRO wants to put Astrosat into its final operating configuration. The scientific payload must be tested and calibrated before starting the research mission. The plan is for the last of the on-board instruments to be switched on 45 days after take-off.

Astrosat - artist's impression
(Image: ISRO)
Astrosat is the first dedicated Indian space observatory that can capture waves in several different band ranges. The mission of the satellite is intended to contribute to a more precise understanding of the universe.

The five instruments with a total mass of 868 kilograms on board Astrosat are intended for use in the areas of visible light, ultraviolet (UV) and in the areas of soft and hard X-rays and can make their observations at the same time. Astrosat has a 120 gigabyte semiconductor storage unit for storing acquired scientific data. If the satellite is in the reception range of the ground station, data can be transmitted to the control center, from where it is transported to the Indian Space Science Data Center (ISSDC) in Byalalu for processing, archiving and further processing.

Astrosat is being prepared for launch
(Image: ISRO)
A large number of Indian institutions are working on the realization of Astrosat. Significant contributions come from ISRO, the Inter University Center for Astronomy and Astrophysics Pune (Inter University Center for Astronomy and Astrophysics, IUCAA), the Tata Institute of Fundamental Research from Mumbai (Tata Institute of Fundamental Research, TIFR), the Indian Institute for Astrophysics Bangalore (Indian Institute of Astrophysics, IIA, also IIAP) and the Raman Research Institute Bangalore (Raman Research Institute, RRI).

In addition to other Indian institutes, two institutions from Great Britain (University of Leicester, UoL) and Canada (Canadian Space Agency, CSA) are also involved in the Astrosat project.

The development of the satellite began in 2004. At the time it was still being thought of a launch in 2007, but this could not be realized due to numerous delays in the Indian space program.

Instrument installation locations and UVIT
(Image: ISRO)
Astrosat should now be able to operate in space on its approximately equatorial orbit for at least five years, and its design was based accordingly. For orbit maintenance and corrective maneuvers, the satellite carries around 43 kilograms of hydrazine, which can be catalytically decomposed in eight single-fuel engines, each with a strength of eleven Newtons.

It is hoped that new knowledge will be gained with regard to energy-rich processes in so-called binary systems, each composed of a black hole and a neutron star. One expects information about the magnetic fields of neutron stars. Regions in which new stars are formed and high-energy processes in star systems outside of our galaxy are to be observed. One wants to record short-lived, bright X-ray sources. Certain areas of the universe are to be scanned in the UV and in the area of ​​hard X-rays.

CZTI - artist's impression
(Image: ISRO)
The imaging double telescope with the designation UVIT for Ultraviolet Imaging Telescope from IIA, IUCAA, ISRO and CSA can perform observation tasks in the near UV (NUV, 200 to 300 nanometers (nm)) and far UV (FUV, 130 to 180 nm), also meet those in the visible light range (VIS, 320 to 550 nm).

The X-ray detector called LAXPC for Large Area X-ray Proportional Counter from TIFR and RRI is intended to record variations in the emission of X-ray sources such as binary systems and active centers of galaxies at energies between 3 and 80 kiloelectron volts (keV). The effective detector area is 8,000 square centimeters (between 5 and 20 KeV). The total detector area is 10,800 square centimeters.

the components of the Soft X-ray Telescope (SXT)
(Image: ISRO)
A telescope for soft X-rays called the Soft X-ray Telescope (SXT) from TIFR, UoL and ISRO is dedicated to studying the variable X-ray spectrum from distant sources at energies between 0.3 and 8 keV. Its effective detector area is in the range of 128 square centimeters (at 1.5 keV) or 22 square centimeters (at 6 keV).

The Cadmium Zinc Telluride Imager, or CZTI for short, from TIFR, IUCAA and ISRO can also work in the area of ​​X-rays. It is sensitive to high-energy X-rays with energies between 10 and 100 keV. The effective detector area is around 480 square centimeters with a total area of ​​973 square centimeters.

The scanner with the designation SMM for Scanning Sky Monitor from the ISRO Satellite Center (ISAC) and IUCAA is intended to observe bright, longer-lasting X-ray sources in binary systems and short-term X-ray bursts. Its three counters for energies between 2.5 and 10 keV are mounted on a rotatable platform that, when set in rotation, enables all regions of the sky in the field of view of the scanner to be sighted once every six hours.

Cubesat structure (here 2U variant)
(Image: Spire)
In addition to Astrosat, six small and micro satellites were launched into space when the PSLV-C30 was launched.

Four of the satellites with the proper names Joel, Peter, Jeroen and Chris are intended to be part of a satellite constellation called Lemur-2 by Spire Global from San Francisco in the USA, which is a system for monitoring ship traffic, called AIS for Automatic Identification System, support and collect weather data.

According to plans by Spire Global, the Lemur 2 constellation is to comprise between 50 and 100 earth satellites in the future. Satellites with a payload for the AIS add a space segment to the system, which enables the reception of position data from watercraft even beyond the range of terrestrial AIS stations.

At sea level, the range of the AIS is between 50 and 100 kilometers. Terrestrial AIS stations exist in different densities along the coastlines, and for example particularly in the area of ​​port facilities and straits. It is estimated that over 70,000 vessels worldwide are equipped with AIS transmitters.

LAPAN-A 2 and position on the PS4 of the PSLV
(Image: LAPAN / ISRO)
The four AIS satellites for Lemur-2 are all 3U cubesats, each have a mass of around four kilograms and are all equipped with two different payloads. SENSE is the name of the AIS receiver on board, STRATOS is the name of the systems for analyzing changes in GPS signals while walking through the earth's atmosphere for the purpose of weather forecasting.

The AIS and Earth observation satellite LAPAN-A 2 alias LAPAN-ORARI from Indonesia comes from the National Institute for Aeronautics and Space (Lembaga Penerbangan dan Antariksa Nasional), Jakarta. It has a box-shaped main body with sides in the range of half a meter.

LAPAN-A 2 is being inspected by members of the Indonesian cabinet
(Image: Secretariat of the Cabinet of the Republic of Indonesia)
Kongsberg Seatex AS from Trondheim in Norway developed the AIS technology for LAPAN-A 2, it is similar to that on board AISSat 1, which has been circling the earth since July 12, 2010.

LAPAN-A 2 with a mass of around 68 kilograms was also equipped with cameras for earth observation and an amateur radio payload.

One of the two camera systems enables a PAL video camera to image areas 80 kilometers wide on the ground. The second camera system, which is experimental in nature and equipped with HDTV technology, was designed for a swath width of 11 kilometers and a resolution of 6 meters.

AIS components on board LAPAN-A 2
(Image: LAPAN)
The amateur radio payload for the amateur radio organization of Indonesia (organasi Amatir Radio Indonesia, ORARI) is equipped with systems for the automated forwarding of data packets (Automatic Packet Reporting System, APRS) and voice messages, the benefits of which are to be demonstrated in particular in dealing with natural disasters and other accidents.

The APRS on board LAPAN-A 2 uses the frequency 145.825 MHz. The speech repeater uses a frequency of 435.88 MHz in the uplink, its transmissions are made on 145.88 MHz. A telemetry radio transmits, as far as planned, on 437.425 MHz.

ExactView 9
(Image: UTIAS)
ExactView 9 aka EV9, mass around 5.5 kilograms, was built by the University of Toronto Institute for Aerospace Studies (UTIAS) from Canada. exactEarth from Cambridge, Ontario, Canada, a subsidiary of COM DEV International Ltd and HISDESAT Servicios Estratégicos S.A., wants to use it as part of an AIS constellation.

The small satellite with a cube-shaped main body - edge length ~ 20 centimeters - is based on a university's own satellite bus and was given the alternative designation NLS-14 in the context of the nanosatellite launch program of ISRO (Nanosatellite Launch Services, NLS).

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Source: exactEarth, ISRO, IUCAA, LAPAN, Spire