22-09-2016, 03:12 PM
Imaging the Sun in the Radio Wavelength using Astronomical Image Processing Software (AIPS)
ABSTRACT
Our project work at Gauribidanur Radio Observatory was primarily on the analysis of the data obtained with the antenna array Gauribidanur RAdio heliograPH (GRAPH) which is a two-dimensional imaging radio interferometric array. The raw data from the back-end instrument (correlator) of the array is converted to FITS (Flexible Image Transport System) format which is then loaded into AIPS for analysis and processing to generate two-dimensional radio images of the Sun. These images will be used to study solar radio emission and its dynamics during different phases of solar activity.
Introduction
AIPS is specially designed to analyze Radio data. It was originally designed by NRAO. It is widely used by VLA, VLBA, VLBI. AIPS is the basic software that can be easily used by an amateur. Though the program is a bit tedious, the outcome is worth the effort.
Methodology
• Converting the raw data into FITS format
• Loading the FITS file in AIPS
• Sorting the data in order
• Provide index to the file
• Listing the data in order
• Plotting the data
• Flagging
• Plotting the flagged data
• Setting flux value
• Antenna calibration
• Applying calibration tables
• Plotting the calibration source
• Imaging the calibrator
• Imaging the source
• Setting contours for extra details
Results
IMAGE ANALYSIS
Before making the image of the Sun, I first make the image of Cygnus, whose data is also collected for 10 minutes. The image of Cygnus is used for calibrating Sun’s image. We calibrate in order to reduce errors like phase errors. Cygnus was chosen for calibration as it’s rising and setting time is almost same as that of the Sun.
RESULTS
The information gathered from the images are:
Plot file version.
• Date and time the file was created.
• Frequency.
• Name of the file.
• Right ascension.
• Declination.
• Peak flux in Jansky/Beam.
The different colors indicate the intensity starting from the most intense represented by red-orange-yellow-light green-dark green-light blue-dark blue-indigo.
The contour image tells us about:
• Plot file version.
• Date and time the file was created.
• Frequency.
• Name of the file.
• Peak flux in Jansky/Beam.
• Shift in degrees.
The contours represent the intensities. Starting from the most intense represented by the innermost contour and decrease in intensity moving outwards.
Hence, with the help of these images we are able to determine the activities on Sun like Solar flares, Solar Radio Bursts, CMEs.
We can also find the movement of these CMEs using the contour image and in turn find the speed of its motion.
We can also determine other parameters like:
• Velocity of the CME
• Brightness temperature
• Electron density
• Flux variations.
CONCLUSION
Astronomical Image Processing Software helps astrophysicists use radio data and convert them into suitable format to produce images. The sources are innumerous since radio sources in the Universe are several. These sources include planets, stars, galaxies, quasars, nebulae, etc. The images helps the scientists to determine and analyze physical parameters like velocity, brightness temperature, electron density and flux variations.
ABSTRACT
Our project work at Gauribidanur Radio Observatory was primarily on the analysis of the data obtained with the antenna array Gauribidanur RAdio heliograPH (GRAPH) which is a two-dimensional imaging radio interferometric array. The raw data from the back-end instrument (correlator) of the array is converted to FITS (Flexible Image Transport System) format which is then loaded into AIPS for analysis and processing to generate two-dimensional radio images of the Sun. These images will be used to study solar radio emission and its dynamics during different phases of solar activity.
Introduction
AIPS is specially designed to analyze Radio data. It was originally designed by NRAO. It is widely used by VLA, VLBA, VLBI. AIPS is the basic software that can be easily used by an amateur. Though the program is a bit tedious, the outcome is worth the effort.
Methodology
• Converting the raw data into FITS format
• Loading the FITS file in AIPS
• Sorting the data in order
• Provide index to the file
• Listing the data in order
• Plotting the data
• Flagging
• Plotting the flagged data
• Setting flux value
• Antenna calibration
• Applying calibration tables
• Plotting the calibration source
• Imaging the calibrator
• Imaging the source
• Setting contours for extra details
Results
IMAGE ANALYSIS
Before making the image of the Sun, I first make the image of Cygnus, whose data is also collected for 10 minutes. The image of Cygnus is used for calibrating Sun’s image. We calibrate in order to reduce errors like phase errors. Cygnus was chosen for calibration as it’s rising and setting time is almost same as that of the Sun.
RESULTS
The information gathered from the images are:
Plot file version.
• Date and time the file was created.
• Frequency.
• Name of the file.
• Right ascension.
• Declination.
• Peak flux in Jansky/Beam.
The different colors indicate the intensity starting from the most intense represented by red-orange-yellow-light green-dark green-light blue-dark blue-indigo.
The contour image tells us about:
• Plot file version.
• Date and time the file was created.
• Frequency.
• Name of the file.
• Peak flux in Jansky/Beam.
• Shift in degrees.
The contours represent the intensities. Starting from the most intense represented by the innermost contour and decrease in intensity moving outwards.
Hence, with the help of these images we are able to determine the activities on Sun like Solar flares, Solar Radio Bursts, CMEs.
We can also find the movement of these CMEs using the contour image and in turn find the speed of its motion.
We can also determine other parameters like:
• Velocity of the CME
• Brightness temperature
• Electron density
• Flux variations.
CONCLUSION
Astronomical Image Processing Software helps astrophysicists use radio data and convert them into suitable format to produce images. The sources are innumerous since radio sources in the Universe are several. These sources include planets, stars, galaxies, quasars, nebulae, etc. The images helps the scientists to determine and analyze physical parameters like velocity, brightness temperature, electron density and flux variations.