Frequently Asked Questions
Common
I am facing issue when trying to download the data by clicking on files. What can be done?
This is usually observed when you are using high latency network. You might try using chrome browser or integrate a download manager with your existing browser.
Also note that if you do not use the website for 30 minutes, it times out. In such a scenario, first login to PRADAN and then resume your download. You may try the 'Bulk Download' feature, instead.
Also note that if you do not use the website for 30 minutes, it times out. In such a scenario, first login to PRADAN and then resume your download. You may try the 'Bulk Download' feature, instead.
I am facing issue when trying to download the data by clicking on Download button. What can be done?
Please take a look at the message displayed above the table, it will guide you appropriately. You may also click on individual files to download the data.
The downloaded zip file does not contain all the files that I selected.
There is a limit defined on the number of file selection based on their sizes. This is also indicated in the warning message which is displayed when trying to download more than the defined limit. You may use the 'Select' feature provided below the data table to help you select the data.
When downloading data, how do I select data to ensure zip volume limits imposed by the application?
You may use the Select feature provided at the end of the payload pages to specify the serial number of the first row that you want to select, then specify the volume of data that is to be selected and then click select. This selects rows continuosly starting from the specified row, and shows you the last selected row in the table. This helps you to know the first row for your next selection.
If you want to select files manually, please use the file size column to know the individual file size and download button displays the limit imposed, to appropriately select the data.
If you want to select files manually, please use the file size column to know the individual file size and download button displays the limit imposed, to appropriately select the data.
After registration and email verification, it shows "Either the page does not exist or you do not have access to this page". How can I get access?
This means that the data access permission is to be assigned to you by the administrator. Please use the 'Contacts' page to reach the administrator.
POLIX
What is the time resolution of POLIX?
The event mode data of POLIX has a time resolution of 10 microseconds.
What is the spectral resolution of POLIX detectors?
POLIX detectors have a spectral resolution of about 20-25%. However, POLIX is not a spectroscopic instrument.
What is the dead time of POLIX processing electronics?
Dead time of POLIX processing electronics is about 60 microseconds.
Is the entire PHA channel range of POLIX useful?
No. Only the 8-30 keV range of POLIX is for source detection. Only background is detected outside this band.
Why the POLIX detectors do not look at the sources directly?
POLIX is a Thomson scattering polarimeter. Therefore, the detectors are designed to detect the X-ray photons scattered from the scatterer. The photons incident through the collimator are not made to directly fall on the detectors.
Why not use a different material (Lithium) or a scintillator as the scatterer?
Lithium scatterer has a lower scattering threshold, hence better. However, it is not viable due to the atmospheric exposure expected during ground testing. A scintillator can be used as a scatterer of higher energy photons, which is outside the POLIX energy range.
What is the duty cycle of POLIX detectors?
POLIX detectors are ON at all times. The high voltage is reduced during the passage of the spacecraft through the South Atlantic Anomaly Region. The Sunlit part of the orbit is used for power generation and data download, and the source observation is carried out mainly during the dark part (earth eclipse) of the orbit. Duty cycle for source observation is about 25%.
Why POLIX has a 3 x 3 Field of View?
It is a balance between two factors: to have one main source within the FoV and not to have very high demand on spacecraft pointing.
What is the photon collection area of POLIX?
The photon collecting area of POLIX is about 650 sq cm. After scattering and absorption in various non-active parts of the system, the telescope has an efficiency of about 1%.
XSPECT
What is the effective area of XSPECT at 6 keV?
There are 16 detectors, each with a geometric area of 4 cm2. One detector is blocked for X-rays, and the remaining 15 have a net effective area of 26 cm2 at 6 keV
What is the spectral resolution of XSPECT?
~170 eV FWHM @ 6 keV @ –35° C
What are the different fields of view (FOV) in XSPECT?
8 detectors having 2° x 2° FOV, 7 detectors having 3° x 3° FOV, 1 blocked detector
What is the time resolution of XSPECT?
The resolution of time stamping is 1 ms.
What is the duty cycle of XSPECT observations?
XSPECT observes sources only when the satellite is eclipsed from the Sun by the Earth. The average duty cycle of source observation is ~25%.
What is the sensitivity of XSPECT?
5σ sensitivity is ~0.2 mCrab for 10 ks of observations
Can I generate L2 products using non-standard filtering?
Yes, XSPECT data processing software is available, which can generate products with userdefined criteria.
Can I add spectra and light curves of the different FOVs?
Light curves can be added for the two FOVs to obtain the net count rate seen by XSPECT (for 15 detectors). However, the spectra of two FOVs should not be added together as they have different ARFs, but rather should be fitted simultaneously.