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.
When should I use the Jump‑To‑File control?
- You are running several large (bulk or ZIP) downloads one after another.
- After each successful download the system shows the name of the last file that was retrieved.
- Before starting the next download, make sure the same filters and sorting you used for the previous download are applied.
- Enter that filename in the Jump‑to‑File box and click Submit.
- The table will be refreshed so the list starts at that file, letting you pick the next batch of files for your bulk or ZIP download.
What exactly does Jump‑To‑File do?
Jump‑To‑File re‑positions the file list so that the first row displayed is the file you entered, based on the current filters and sort order. It simply updates the view to help you select the next batch of files for bulk or ZIP downloads.
Tip for speedy results: using the default sorting (usually ID‑descending) yields the most performant response.
The downloaded zip file does not contain all the files that I selected. Why?
There is a per‑ZIP limit. When your selection exceeds the limit, the system only includes files up to that threshold.
The UI shows the name of the last file that was added to the ZIP.
To get the remaining files:
- Copy that filename.
- Paste it into the Jump‑To‑File input (found at the bottom‑left of the download page).
- Click Submit – the list will start from that file, letting you pick the next batch.
Alternative: Use the Download in Bulk button, which bypasses the ZIP‑size limit by streaming files individually.
When downloading data, how do I select data to ensure zip volume limits imposed by the application?
You may use the Select feature to specify the size (in MB) that you want to download and also specify the serial number of the first row that you want to select the data from, then submit your request. This selects data continuosly starting from the specified row. Additionally, it shows you the last selected filename, to help you select data for the next zip download.
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.