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.
CLASS
How do we select data with XRF signals?
Find flare times from GOES satellite X-ray flux and enter the UTC times as query for downloading.
How to get the footprint corresponding to the downloaded files?
The latitude and longitude of the four corners of the footprint are provided in the header of the data file.
What to do if there is no corresponding XSM data?
We are using GOES-XRS data to derive temperature and emission measure of the solar flare with which a solar spectrum is simulated in XSPEC using the CH2-XSM response matrices.
Can I use any other X-ray spectroscopy analysis package?
The data files and response matrices are compatible with XSPEC. It may need modification for compatibility with other software packages.
XSM
Why XSM observations of the Sun are available only for few months?
XSM observes the Sun whenever it is within the instrument's field of view. The dawn-dusk seasons (around mid August to mid November and mid February to mid May) are primary observing period for XSM when there is good coverage. During the rest of the periods (noon-midnight season) observations are sparse. Data for first observing season are available now.
Why some times there are gaps in the XSM lightcurves?
Such gaps may arise due to multiple reasons - during noon-midnight season, the Sun remains in the field of view of XSM for a short duration in every orbit resulting on long gaps; during beginning and end of the dawn-dusk season, the Sun gets occulted by the Moon for short duration every orbit; during the middle of the dawn-dusk season when the continuous Sun observations are expected, sometimes the spacecraft attitude changes due to operational reasons results in the Sun going out of field of view; in some cases, the gaps arise due to the data corruption during transmission. The XSMDAS takes care of all such gaps by defining GTI (good time interval) for solar observations.
During low solar activity, light curves at higher energies show periodic variations at orbital frequency. What is the reason behind this?
As the Sun's position in the field of view of XSM changes during the course of the orbit, the corresponding effective area and thus measured X-ray count rate also changes. The XSMDAS applies the effective area correction to estimate the incident count rate. During low solar activity, the X-rays at higher energies are mostly due to background arriving from the entire field of view. Hence, the effective area correction results in the periodic variations in backgorund lightcurve at higher energies. Such variations indicate that the solar X-ray flux is lower than background, and hence such light curves should not be used for any solar analysis. For further details please refer to this paper.
For XSM spectra obtained during low solar activity, count rate at higher energies are below one of the background spectrum provided. In such cases, how to carry out spectroscopy?
The non solar X-ray background in XSM shows slight variation depending on the attitude configuration of the Chandrayaan-2 spacecraft as discussed in the In-flight performance paper. This may result in such situation. Generally, it is recommended that the spectroscopy to be attempted only in the energy range with the solar X-ray count rate is above the non-solar X-ray background. In case of any specific requirement including background dominated energy range, please consult XSMPOS first.
IIRS
How many types of PDS4 Data Products are available for download?
There are two types of products available for download - raw and calibrated. For more information kindly refer to file naming convention of Ch2 iirs dp archive and sis document.
How can I extract the information of product?
For each level of product there is corresponding XML label file. We can deduce basic information like datatype, no. of lines, no. of samples and bands
How to open the data products?
As the raw and calibrated data products are provided in generic binary qube image data along with label file and it can be imported with any image viewer software.
What will be the contents of downloaded zip?
When we unzip the zip file, we see three folders data,geometry and browse. Based on the type of data products, the data folder contains directory/folders i.e. raw and calibrated. For more information kindly refer to file naming convention of Ch2 iirs dp archive and sis document.
When we unzip the product we see date folder what does it signify?
The date folder signifies the imaging date when the product is acquired. Morever the date and time of acquisition can be deduce from zip file. For e.g. ch2_iir_nci_20191202T0639493114_d_img_d18.zip signifies that the product was acquired on 02 December 2019 at 06:39:49.3114 UTC
How to use the data products?
Kindly refer to Ch2 iirs dp archive and sis document and data product user guide under Other Downloads section
Where to find Ch2 iirs dp archive and sis document ?
Browse to Other Downloads and go to iir. Download iir.zip and unzip it. Ch2 iirs dp archive and sis document resides in document directory.
CHACE-2
How to search a particular data files from the list
Enter the observation time in appropriate field and click filter button.
How to verify if the content of zip file is completely downloaded
Please check the size/checksum of zip file with details provided in the corrosponding xmlfile
DFRS
What is the prime objective of DFRS experiment?
To study the variations in the ionosphere/atmosphere of Moon
What are the two frequencies used in DFRS experiment?
Two coherent frequencies are X (8496) and S (2240 MHz) bands
What is the basic principle of radio occultation experiment?
The RO experiment relies on the principle that the phase of a radio signal, propagating from a satellite to the ground station, gets perturbed when it crosses through the planetary/lunar atmosphere or ionosphere
What is the resolution in altitudinal profile can be expected in RO experiment?
Approximately 100 m
What are the calibrated data products of DFRS experiement?
Year–DOY, Second of the Day, Transmitted frequency in Hz, Observed frequency in Hz (received Doppler + transmitted frequency), Expected frequency in Hz ( theoretical Doppler + transmitted frequency) and frequency residual ( Observed frequency -Expected frequency)
SAR
The DFSAR data products has only one Frequncy Band Why?
The prime objective of the SAR is to cover the Lunar Polar Region in L-Band Full polarisation mode, only L-Band Acquisions made till now. Dual Band acquisitions are expected in future.
How to know whether the product downloaded is Full Polarization,Circular Polarization or Dual Polarization?
Polarization of products downloaded will be deduced from file name. For e.g. ch2_sar_ncls_20200516t013453432_d_cp_d18.zip signifies circular polarization(cp) product. For more information kindly refer to file naming convention of CH2DFSAR DPSIS document.
How can I extract the information of product?
For each level of product there is corresponding XML label file. We can deduce basic information like datatype, no. of lines and no. of samples
How to open the data products, is there any software avialable for analysis?
Please use MIDAS Software for analysis. As the basic products are provided in GeoTiFF format , we can utilise any general purpose processing tools for visualising the products e.g. ENVI/QGIS.
What will be the contents of downloaded zip?
When we unzip the zip file, we see three folders data,geometry and browse. The data folder contains all products i.e. sli , sri and gri for calibrated and raw files for raw product, geometry folder contains geometry information and browse folder contains browse image
When we unzip the product we see date folder what does it signify?
The date folder signifies the imaging date when the product is acquired. Morever the date and time of acquisition can be deduce from zip file. For e.g. ch2_sar_ncls_20200516t013453432_d_cp_d18.zip signifies that product was acquired on 16 May 2020 at 01:34:53 UTC
What does sli, sri and gri signifies?
sli stands for single look complex image , gri stands for ground reference image and sri stands for seleno referenced image. For more product information, kindly refer to CH2DFSAR DPSIS document
How to use the data products?
Kindly refer to CH2DFSAR DPSIS document
Where to find CH2DFSAR DPSIS document ?
Browse to Other Downloads and go to DFSAR. Download SARLTA.tar and unzip it. DPSIS document resides in document directory.
OHRC
How many types of PDS4 Data Products are available for download?
There are two types of products available for download - raw and calibrated. For more information kindly refer to file naming convention of Ch2 ohrc dp archive and sis document.
How can I extract the information of product
For each level of product there is corresponding XML label file. We can deduce basic information like datatype, no. of lines and no. of samples
How to open the data products?
As the raw and calibrated data products are provided in generic binary image data along with label file, it can be imported with any image viewer software.
What will be the contents of downloaded zip?
When we unzip the zip file, we see three folders data,geometry and browse. Based on the type of data products, the data folder contains directory/folders i.e. raw and calibrated. For more information kindly refer to file naming convention of Ch2 ohrc dp archive and sis document.
When we unzip the product we see date folder, what does it signify?
The date folder signifies the imaging date when the product is acquired. Morever the date and time of acquisition can be deduced from zip file. For e.g. ch2_ohr_ncp_20200824T1003365280_d_img_d18.zip signifies that the product was acquired on 24 August 2020 at 10:03:36.5280 UTC
How to use the data products?
Kindly refer to Ch2 ohrc dp archive and sis document
Where to find Ch2 ohrc dp archive and sis document ?
Browse to Other Downloads and go to OHR. Download OHR.zip and unzip it. Ch2 ohrc dp archive and sis document resides in document directory.
TMC-2
How can I extract the information of product?
For each level of product there is corresponding XML label file. We can deduce basic information like datatype, no. of lines and no. of samples
How to open the data products?
As the raw and calibrated data products are provided in generic binary image data along with label file, it can be imported with any image viewer software. Derived data products - DEMs and Ortho are provided in GeoTiFF format, we can directly open the products using ENVI/ERADAS.
What will be the contents of downloaded zip?
When we unzip the zip file, we see three folders data, geometry and browse. Based on the type of data products, the data folder contains directory/folders i.e. raw, calibrated, and derived. For more information kindly refer to file naming convention of Ch2 tmc2 dp archive and sis document.
When we unzip the product we see date folder, what does it signify?
The date folder signifies the imaging date when the product is acquired. Morever the date and time of acquisition can be deduce from zip file. For e.g. ch2_tmc_nrn_20191206T0712227064_d_img_d18.zip signifies that product was acquired on 06 Dec. 2019 at 07:12:22.7064 UTC.
What does dtm, oth and grd signifies?
dtm stands for digital terrain model ,oth stands for ortho image and grd stands for seleno referenced grid data. For more product information, kindly refer to Ch2 tmc2 dp archive and sis document.
How to use the data products?
Kindly refer to Ch2 tmc2 dp archive and sis document.
Where to find Ch2 tmc2 dp archive and sis document?
Browse to Other Downloads and go to TMC. Download TMC.zip and unzip it. Ch2 tmc2 dp archive and sis document resides in document directory.
SPICE
What are the Pre-requisites for using this dataset?
The user is expected to have a working knowledge of the SPICE Toolkit since all data in the dataset is in form of SPICE kernels
How is the data organized in this dataset?
This dataset contains the monthly kernel files for the Spacecraft ephemeris and attitude information and a single Spacecraft clock kernel file alongwith some other supporting kernels.