Python Sso_freeze User Guide Sso Freeze
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Python sso_freeze User Guide By Dale Weigt D.M.Weigt@soton.ac.uk Contents • • Hardwire Locations Using Python sso_freeze: – Section 1): Reading in the Chandra events file – Section 2): Reading in the orbit empheris file – Section 3): Reading in the horizons2000 file – Section 4): Applying the corrections to the photon position – Section 5): Creating the new corrected fits file • Other comments 2 Hardwire Locations • The code is split into 5 sections (labelled and with a brief explanation about each within the script). • Sections 1), 2), 3) and 5) require a file to be hardwired. • Section 1) -> evt_location -> input the path of the event file to be corrected. • Section 2) -> orb_location -> enter path of the orbit empheris file of the spacecraft. 3 Hardwire Locations • Section 3) -> eph_location -> enter path of chandra_horizons2000 file needed (from horizons2000 folder). • Section 5) -> new_evt_location -> enter path of the new corrected fits file to be written with corrections. 4 Using Python sso_freeze • The next few slides will talk about how to use the code in sections. • Once the files are hardwired, the code basically does all the work without any more input required by the user. • The code is commented throughout, explaining what each variable is. • For new Python users, the very first section imports all the relevant modules needed to run the function within the script/Jupyter notebook. 5 Section 1): Reading in the Chandra event file • Make sure the event file is hardwired before running the code! – this is at the beginning of the section. • The event file pre-correction should look similar the event file below – distinguishable streaks across the detector (as Jupiter moves very fast when viewed from Chandra). ObsID 18608 6 Section 1): Reading in the Chandra event file • Once the file is read in, the header information and data needed for analysis is extracted: – the time of each photon observed, – start time and date of the observation, – the x and y position of Jupiter with it’s corresponding RA and DEC and the start of the observation. • With the date and time information, the Day of Year (DOY) when Chandra was making the observations is calculated – using a defined function at the beginning of the script, doy_frac. 7 Section 2): Reading in the orbit empheris file • Make sure the orbit empheris file is hardwired before running the code! – this is at the beginning of the section. • When the orbit empheris file is read in, like before, the relevant header information is extracted: – Time of observation when the Jovian photons reach the spacecraft – Positional coordinates of space craft at the time when the photons were detected • The start time of obs is subtracted from the time found in the orbit empheris file to allow the DOY of the spacecraft to be calculated. 8 Section 3): Reading in the horizons2000 file • Make sure the Chandra_horizons2000 file is hardwired before running the code! – this is at the beginning of the section – files found from horizons2000 folder. • If you are using your own generated file, ensure that the table settings are of the following form: • The files do not to be edited to account for the time to be read into sections – Pythons has in built-in modules to carry this out! 9 Section 3): Reading in the horizons2000 file • The code automatically locates the empheris file data needed and reads in the columns needed – again, any size horizons2000 file can be read in! • The date, time, RA and DEC of Jupiter at each specified interval is read in and the DOY of the horizons2000 file is calculated. • If the date lies within a leap year, the DOY is corrected and this is used instead. 10 Section 4): Applying the corrections to the photon position • The code takes the positional coordinates and DOY from Section 2) and performs a 1D-linear interpolation to the DOY from the horizons file. • This produces the new orbital positional coordinates within this time range. • This is used to calculate the positional coordinates of Jupiter during the observation with the corresponding RA and DEC. • The offset from Jupiter was also calculated (denoted as cc in the script/Jupyter notebook). 11 Section 4): Applying the corrections to the photon position • An interpolated RA and DEC is calculated from interpolating the RA/DEC and DOY from Section 3) to the DOY of Chandra (calculated from Section 1). • The values are then used to calculate the corrected position of the photons i.e track them back to Jupiter’s disk and auroral regions. 12 Section 5): Creating the new corrected fits file • Make sure the file path of the new fits file is hardwired before running the code! – this is at the beginning of the section. • The code retrieves the data and header information from the original fits file and changes the x and y coordinates to the corrected positional coordinates. • The corrected fits file is then written as a new file – therefore the original fits file is not overwritten. 13 Section 5): Creating the new corrected fits file • The final result should look something similar to below – two clear North and South x-ray regions! ObsID 18608 14 Other comments • The python code was translated from the stop_hrci IDL script created by Randy Gladstone. • The python code produces the same result as the IDL script without having to overwrite the original file and making edits the horizons2000 file. • The plot at the end was used for a sanity check – to check the data was interpolated correctly. • The figure can be saved if needed but it is not essential for the code to run. 15 Other comments • Future steps: – To further optimise the code -> no need to hardwire files and possibly extract the files from a library with the associated ObsID. – Translate the other IDL scripts into Python too. – Will all be on Github and will be made public. – Github repository with the script(s): https://github.com/waledeigt/zeno-py.git 16
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