AstroSat Picture of the Month of Jan, 2019

AstroSat Picture of the Month of Jan, 2019

The 97 minute orbit of AstroSat around the Earth. The orbit is roughly equatorial (top right), inclined at around 6 degrees to it (top left). This results in each orbit being slightly displaced from the previous one (bottom). Pic Credits: Leo Jackson John, Operation Director, AstroSat, ISTRAC, ISRO

When seeing images from AstroSat, have you ever wondered where exactly is the satellite, how does it move, and how do astronomers get their hands on the data? This month's APOM is here to answer those questions for you.

AstroSat was launched https://www.youtube.com/watch?v=hZCRiNpfB-8 by ISRO on 28 September, 2015 from Sriharikota https://www.isro.gov.in/about-isro/satish-dhawan-space-centre-sdsc-shar, on board the PSLV-C30 into its current orbit. This is a low-earth equatorial orbit, at a height of 650 km above the Earth. This orbit is not exactly over the equator, but is inclined at angle of about 6 degree to it.  In the top left image, the green line marks the equator and the yellow line marks the orbit of AstroSat and the top right image is a view from over the north pole. But why was this orbit chosen?

Our Earth has a magnetic field (https://en.wikipedia.org/wiki/Earth%27s_magnetic_field), which behaves overall like a bar magnet (http://hyperphysics.phy-astr.gsu.edu/hbase/magnetic/MagEarth.html), with its poles a few degrees from the poles defined by our rotation. These magnetic fields trap charged particles within them, which form the Van Allen belts (https://www.space.com/33948-van-allen-radiation-belts.html). These belts are much closer to the Earth over the southern Atlantic Ocean. An equatorial orbit reduces the effect of this South Atlantic Anomaly  https://en.wikipedia.org/wiki/South_Atlantic_Anomaly, on AstroSat which carries very sensitive instruments. Making the inclination exactly zero requires more resources and hence a 6 degree inclination was chosen.

AstroSat takes about 97 minutes to orbit the Earth once. Hence, it will not pass directly overhead the same point in successive orbits. Each orbit, therefore, will be slightly shifted with respect to the previous one. The individual orbits shown in red in the bottom image mark orbits. One orbit per week is plotted for clarity. Data is beamed down from an antenna on the satellite once every orbit, when it passes over India. The data is received by ISRO's dedicated Indian Deep Space Network http://isrohq.vssc.gov.in/VSSC_V4/index.php/ground-segment/82-chandrayaa... antenna in Byalalu https://en.wikipedia.org/wiki/Indian_Deep_Space_Network near Bengaluru (marked as BLR). All orbits of AstroSat fall within the visibility of this antenna, which is marked by a circle centred at Byalalu. ISRO can also use an antenna in Indonesia, marked BIK, to monitor the satellite when needed. All the command, control and tracking of AstroSat is done by ISTRAC https://www.isro.gov.in/about-isro/isro-telemetry-tracking-and-command-n... in Bengaluru.

As of 30 January 2019, AstroSat has completed more than 18,000 orbits around the Earth, acting as our high energy eye,  uncovering the nature of neutron stars, black holes, hot star, and many strange celestial objects. May it continue to do so for many more orbits!

PSLV-C11/ Chandrayaan-1

PSLV-C11 Brochure

Chandrayaan-1

Chandrayaan-1, India's first mission to Moon, was launched successfully on October 22, 2008 from SDSC SHAR, Sriharikota. The spacecraft was orbiting around the Moon at a height of 100 km from the lunar surface for chemical, mineralogical and photo-geologic mapping of the Moon. The spacecraft carried 11 scientific instruments built in India, USA, UK, Germany, Sweden and Bulgaria.

After the successful completion of all the major mission objectives, the orbit has been raised to 200 km during May 2009. The satellite made more than 3400 orbits around the moon and the mission was concluded when the communication with the spacecraft was lost on August 29, 2009.

प्रमोचन भार / Launch Mass: 

1380 kg

मिशन कालावधि / Mission Life : 

2 years

शक्ति / Power: 

700 W

प्रमोचक राकेट / Launch Vehicle: 

PSLV-C11

उपग्रह का प्रकार / Type of Satellite: 

Science & Exploration

निर्माता / Manufacturer: 

ISRO

स्‍वामी / Owner: 

ISRO

अनुप्रयोग / Application: 

Planetary Observation

कक्षा का प्रकार / Orbit Type: 

Lunar

PSLV-C11/ Chandrayaan-1 Gallery

 

Scanning Sky Monitor (SSM) Payload onboard AstroSat made Operational

The Scanning Sky Monitor (SSM) will monitor the transient X-ray sky to detect and locate X-ray sources in its large Field Of View (FOV).  It comprises three almost identical detector units each with a 1D coded-mask and the respective electronics. All the three modules of SSM are mounted on a single platform capable of rotation.  A photograph of the SSM payload on is shown here below in figure 1. The Processing Electronics and the Platform motor drive electronics are placed inside the spacecraft body.  

Figure 1: SSM with three cameras and associated front end electronics.

SSM platform deployment was done on the day of launch after spacecraft injection into the intended orbit, soon after solar panel deployment.
On Day 2 and Day 3 (September 29 & September 30, 2015) operations related to SSM platform rotation were carried out successfully, as planned.  All the modes of rotation were checked and the parameters were verified.

Scanning Sky Monitor (SSM) onboard AstroSat has been operational since October 12th 2015, on the 15th day after the successful launch of AstroSat on 28th September 2015.

The temperatures of all the packages of the payload have been within the expected limits.  Spacecraft was oriented in such a way that the well-known X-ray source “Crab” was positioned at the centre of Field Of View (FOV) of two of the SSM units, SSM1 and SSM2, which have a crossed FOV. 
SSM1 was powered ON first and all the health parameters of the unit were monitored and found satisfactory. High Voltage (HV) to the anodes was increased step by step to the required value with constant monitoring of telemetry parameter.  Once the required HV step was attained in the SSM1 unit, the counts detected by the unit were indicated in the telemetry.  It was exciting to observe the expected count rates in the telemetry as soon as the HV was raised to the required step. 
The data from SSM1 unit was played back in the subsequent orbit and analysed for the light curves and spectra from all anodes in that unit. 
The SAA entry and exit operations to lower the HV of the unit for safe operations were handled with macros on-board.  The prompt execution of these macros during the non-visibility period during the passage through SAA region can be seen in the later part of the light curve.
Following the successful power ON of SSM1 unit the other two units – SSM2 and SSM3 were also powered ON, two orbits later during the visibility period. All the health checks were found satisfactory.  The units were powered ON one after the other.  The data play back was done in the subsequent orbits.  Performances of these two units were also as expected.  

SSM First light of Crab - a Neutron Star  - on 12th October 2015

The sky image observed by SSM with its first observation with Crab at the centre of its FOV is shown here in figure 2.  “Crab” was detected at the centre of the FOV as expected.

Figure 2: First light from SSM with Crab at the centre of the FOV

SSM First light of GRS 1915+105 - a Black Hole  - on 14th October 2015

Following this, SSM was maneuvered to a field that contains the enigmatic Galactic Black Hole source GRS 1915+105. Even with many challenges on mission operations, AstroSat was oriented to the required field with GRS 1915+105 in the FOV of SSM on October 14th, 2015. THANKS to mission operations team!
The particular field was crowded with few other bright sources (eg. Cyg X-1, Cyg X-2, Ser X-1), while GRS 1915+105 was the strongest source with intensity ~2 Crab. GRS 1915+05 also displays very peculiar, but ‘structured’ X-ray variability known as ‘class’. 

Figure 3: AstroSat – SSM First light of the enigmatic Black Hole GRS 1915 + 105

AstroSat-first light from Galactic Black Hole GRS 1915+105 as observed by SSM is shown in figure 3.  A quick look of the variability profile of the light curve matches well with one of the earlier observations of the source with NASA's Rossi X-ray Timing Explorer (RXTE) satellite as shown in the figure. More detailed analysis results will follow.

SSM – Indication of a M - class Solar Flare  - on 16th October 2015

During a scheduled flux calibration observation with SSM pointed to Crab, during a specific part of the orbit, at ~6:12 UT, October 16th 2015, SSM (all three detectors) recorded a sudden upsurge in counts – with a rise time of ~2 minutes and a decay time of ~18 minutes as shown in figure 4.

Figure 4: SSM observations with Earth in its FOV on October 16, 2015 during a M-class Solar Flare at 6:10 UT

Figure 5: GOES observations of M-class Solar flare at 6:10 UT on 16th October, 2015.

This occurred when the pointing of the SSM cameras was facing the Earth such that the FOVs of all the three cameras had Earth within.  The Sun was almost 180 degrees away. .  The upsurge in counts was understood to be X-rays due to a M-class Solar flare, which was confirmed with the time of occurrence, type of flare etc. from the US satellite “GOES” data.  The correlation of the time of detection of upsurge of counts in SSM and the time of occurrence of the flare can be observed from both the figures - 4 and 5. 

ASTROSAT - ISRO

ASTROSAT is India’s first dedicated multi wavelength space observatory. This scientific satellite mission endeavours for a more detailed understanding of our universe. One of the unique features of ASTROSAT mission is that enables the simultaneous multi-wavelength observations of various astronomical objects with a single satellite.

ASTROSAT observes universe in the optical, Ultraviolet, low and high energy X-ray regions of the electromagnetic spectrum, whereas most other scientific satellites are capable of observing a narrow range of wavelength band. Multi-wavelength observations of ASTROSAT can be further extended with co-ordinated observations using other spacecraft and ground based observations. All major astronomy Institutions and some Universities in India are participating in these observations.

ASTROSAT with a lift-off mass of about 1513 kg was launched into a 650 km orbit inclined at an angle of 6 deg to the equator by PSLV-C30. After injection into Orbit, the two solar panels of ASTROSAT were automatically deployed in quick succession. The spacecraft control centre at Mission Operations Complex (MOX) of ISRO Telemetry, Tracking and Command Network (ISTRAC) at Bangalore manages the satellite during its mission life.

The science data gathered by five payloads of ASTROSAT are telemetered to the ground station at MOX. The data is then processed, archived and distributed by Indian Space Science Data Centre (ISSDC) located at Byalalu, near Bangalore.

The scientific objectives of ASTROSAT mission are:

• To understand high energy processes in binary star systems containing neutron stars and black holes
• Estimate magnetic fields of neutron stars
• Study star birth regions and high energy processes in star systems lying beyond our galaxy
• Detect new briefly bright X-ray sources in the sky
• Perform a limited deep field survey of the Universe in the Ultraviolet region

Payloads of ASTROSAT :

Five payloads of ASTROSAT are chosen to facilitate a deeper insight into the various astrophysical processes occurring in the various types of astronomical objects constituting our universe.  These payloads rely on the visible, Ultraviolet and X-rays coming from distant celestial sources.

1. The Ultraviolet Imaging Telescope (UVIT), capable of observing the sky in the Visible, Near Ultraviolet and Far Ultraviolet regions of the electromagnetic spectrum
2. Large Area X-ray Proportional Counter (LAXPC), is designed for study the variations in the emission of X-rays from sources like X-ray binaries, Active Galactic Nuclei and other cosmic sources.
3. Soft X-ray Telescope (SXT) is designed for studying how the X-ray spectrum of 0.3-8 keV range coming from distant celestial bodies varies with time.
4. Cadmium Zinc Telluride Imager (CZTI), functioning in the X-ray region, extends the capability of the satellite to sense X-rays of high energy in 10-100 keV range.
5. Scanning Sky Monitor(SSM), is intended to scan the sky for long term monitoring of bright X-ray sources in binary stars, and for the detection and location of sources that become bright in X-rays for a short duration of time.

PSLV-C44(ON 24-JAN-2019)

PSLV-C44

India’s Polar Satellite Launch Vehicle (PSLV), in its 46th flight, will launch the Kalamsat and Microsat-R from the First Launch Pad (FLP) of Satish Dhawan Space Centre SHAR, Sriharikota on January 24, 2019.

PSLV is a four stage launch vehicle with alternating solid and liquid stages. The PSLV with 2 strap-on configuration has been identified for this mission and the configuration is designated as PSLV-DL. PSLV-C44 is the first mission of PSLV-DL and is a new variant of PSLV.

In PSLV-C44, the fourth stage (PS4) of the vehicle will be moved to higher circular orbit so as to establish an orbital platform for carrying out experiments. Kalamsat, a student payload will be the first to use PS4 as orbital platform.

PSLV-C44 will also carry Microsat-R, an imaging satellite.

PSLV-C44 Gallery

PSLV-C44 Curtain Raiser Video (English)

PSLV-C44 Curtain Raiser Video (Hindi)

PSLV-C44 Launch Brochure

https://drive.google.com/file/d/1yg6_HFXRJIC7br3phJMQXoigGqCVh06A/view?usp=sharing

PSLV-C44 Launch Kit

https://drive.google.com/file/d/1CBsEfPEHWXFxefa48i6UvMW4Sxkh0AAi/view?usp=sharing

Stay tunned for new updates..................!!!!!!!!!!!!!!!!!!!!!!!!!!

I am pretty sure that this rocket named PSLV C-44 gonna launch successfully by our scientists from Satish Dhawan Space Center Sriharikota TODAY(24-jan-2019)