SSM onboard ASTROSAT - Results and plan ahead

M. C. Ramadevi

ASTROSAT, 1 year Celebrations, IUCAA, Pune

●  Detect and locate transient sources

●  Long-term time variability

●  Transient Alert generation

●  Catalog

Angular resolution – expected 12 arcmin; - Observed - Confined within a pixel (12 arcmin X 2.5 deg)

Crab in SSM FOV (First orbit data)

Crab in SSM 1, 2, 3 FOV

- Crab at the expected locations in all three units - Observed at various positions in FOVs of each unit

Astronomer's Telegram ATel#8185 generated on the above detection of variability in GRS 1915+105

SSM – GRS 1915+105 (3rd day obs) Black Hole source Observations; Oct 15, 2015

β-Class variability Hardness Intensity of GRS 1915+105

SSM Observations of an X-ray pulsar 4U0115+63

Observed on October 26, 2015

Pulsations from binary X-ay pulsars

Cen X3 4.8+/- 0.25 s

Vela X1 283+/-0.8 s

Anode spectra

Crab spectra in first three PV phases observations

Black – Oct. 12Th , 2015 Red – Nov 6th, 2015 Green – Jan 15th, 2016

Mask-weighted spectrum extraction – to be done

SSM Light curves ➢  Data filteration – Good Time Intervals –

removal of earth occult, SAA regions etc. ➢  Calibration factors for obtaining DPHs ➢  Position Resolution parameter ➢  Imaging algorithms – different approaches ➢  spacecraft attitude variations ➢  Cross checks of the flux extracted ➢  T&E of SSM website at ISSDC needs to be

done

Smearing of DPH probably due to attitude variations

Simulated DPHs for attitude variations

SSM Crab light curve

➢ 10 min stares – flux extracted ➢ Flux extracted in few of the stares go as low as few hundred mCrab,which are not shown here Variations could be related to space craft attitude variations (data in Jan 2016)

➢ 10 min stares – flux extracted ➢ Flux extracted in few of the stares go as low as few hundred mCrab,which are not shown here ➢ Variations could be related to space craft attitude variations (data in Jan 2016)

SSM Crab light curve

Why it took so long and still in process....? ➢  Data processing – data pipeline software

➢  New requirements introduced after launch ➢  Any issues with raw data – data quality checks – routine tasks ➢  Data dissemination – to anyone in the team as and when required ➢  Commands and operation related to SSM platform rotation ➢  Interface software with mission – like discussions on the aux data, earth occult details etc. ➢  PV phase planning – interaction with mission team ➢  Implementation of any caldb database in the imaging code ➢  Imaging code – different approaches – SUB-PIXEL Imaging ➢ In addition parallely ➢ Calibration aspects ➢ Fine tuning of calibration parameters ➢ Immediate checks of the data for various science aspects ➢ Parallel codes were written for data analysis till the data-pipeline

was made available

SSM2 is OFF

Out of three units, SSM2 is OFF, as it developed a leak since Feb 15, 2016 and operated till Aug 17th, 2016 with a reduced HV. However, since SSM2 is one of the edge Cameras and would be scanning the part of the sky which SSM1 does, the duty cycle of SSM has not reduced largely.

Out of three units, SSM2 is OFF, as it developed a leak since Feb 15, 2016 and operated till Aug 16t

Feb 15, 2016

Plan ahead ➢  Imaging with data since April 2016, as the spacecraft

attitude control is better

➢  Analysis of all data sets to extract light curves of the sources observed

➢  Expected to make lightcurves available at ISSDC in a month's time. (Oct 6 & 7 T&E at ISSDC for SSM website and data flow will start)

➢  Fine tuning of calibration constants and fine tuning of the error in the flux extracted

➢  Looking forward to interesting discoveries and dedicated Xray sky survey with SSM

Thank You..