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.
VELC
Why spectroscopic observations of the solar corona at the wavelength of 5303Å?
The profiles of the forbidden emission lines in the solar coronal spectrum centered at the wavelength of 5303Å (FeXIV) contain information on the physical parameters such as temperature and density in the corona.
What is unique with VELC spectroscopic observations?
In VELC, spectroscopic observations are carried out with multi-slit spectrograph which covers the field of view (FoV) in the heliocentric distance range from -1.5Ro to +1.5Ro (1Ro = radius of the Sun or its photosphere). By convention, the -ve sign indicate regions to the east and south of center of the Sun. The +ve sign indicate regions to the west and north of center of the Sun respectively. The region of the FoV between center of the Sun and 1.05Ro will be covered by the occulting disk in the VELC. Hence solar corona very close to the limb of the solar photosphere (i.e. from 1.05Ro) till 1.5Ro can be observed. There are four slits in VELC. These observe different regions of the solar corona simultaneously. The pixel and spectral resolution are ~1.25”/pixel and ~0.0283Å, respectively.
What are the different types of observational modes in the VELC spectroscopy channel?
There are two modes of observations possible in the VELC spectroscopy channel. They are Sit-Stare mode (SS) and Raster-Scan mode (RS).
What is Sit-Stare mode of observations?
In Sit-Stare mode, each of the four slits in the VELC spectrograph channel will observe a particular region of the corona between 1.05Ro and 1.5Ro The region and duration of observations will be provided by the user. Each slit in its fixed position will observe from -1.5Ro to +1.5Ro in the north-south direction of the Sun. In the east-west direction, the extent of the corona that will be observed is ~0.01Ro.
What is Raster scan mode of observations?
In Raster-scan mode, the four slits will scan the entire FOV (-1.5Ro to +1.5Ro) of the solar corona. Two-dimensional images can be obtained by combining data from all the four slits. Slit-1 will scan the distance range -1.5Ro to 0.75Ro in the east-west direction of the Sun.; slit2 for -0.75Ro to 0Ro; slit3 for 0Ro to +0.75Ro; and slit4 for +0.75Ro to +1.5Ro. In each position, all the slits will observe from -1.5Ro to +1.5Ro in the north-south direction of the Sun. The instantaneous width of the coronal region that would be observed in the east-west direction for each slit position is ~0.01Ro.
How many headers are there in FITS spectra?
There are four different headers in FITS file. They are Basic header, Instrumental header, Satellite header and Observational header.
What is bit error in the data?
While downloading data from the spacecraft to ground, there can be some transmission loss. In VELC, the data in each row of the detector array will be downloaded one after the other. If data in any row(s) got lost during reception, it is called bit-error. The corresponding rows will be packed with ‘zeros’ during generation of Level-1 data from Level-0 data. The bit error row numbers will be mentioned in the Observational header of the FITS file.
What is Snapshot mode/Frame binning mode of observation?
If the detector is configured for observations with exposure time as 2sec and cadence as 10sec, then five images or spectra would be recorded in 10sec. In Snapshot mode, the fifth image alone will be saved in the onboard memory. If it is in Frame-binning mode, all the five images will be added in the onboard memory to generate one image. The latter final image alone will be saved.
What is meant by merging of top and bottom ports of data?
In VELC, CMOS detectors are used. By design, they have two halves. These are termed top and bottom ports. The two ports have separate readouts. The corresponding data will be also downloaded seperately. During generation of Level-1 data from Level-0 data, these top and bottom ports data will be merged to get data for the entire detector array.
What is meant by “removing inactive pixels”?
By design, the size of the CMOS detector used in VELC is 2192 x 2592 pixels. The first and last set of 16 rows and columns in the aforementioned two-dimensional array of pixels will be inactive for the input signal. They are named as “inactive pixels”. These pixels will be removed during generation of Level-1 data from Level-0 data. Hence Level-1 FITS data will be of size 2160 x 2560 pixels.
What is Window mode of observation?
In VELC, window mode means observations of the Region of Interest (RoI). The detector size is 2160 x 2560 pixels as mentioned above. In this two-dimensional array of pixels, there is provision onboard to read the data in the pixel number range of either (0:1080, 0:2560) or (1080:2160, 0:2560) or (0:2160, 0:1280) or (0:2160, 1280:2560).
What is meant by “Alternate/Simultaneous gain”?
In VELC, there is provision to choose the gain of the detector. The possible gains are 1x or 2x (which are termed as Low Gain) and 10x or 30x (which are termed as High Gain). User can choose any one of the following combinations: [1x,10x] or [1x,30x] or [2x,10x] or [2x,30x]. If simultaneous gain option is selected, then both low and high gain data as per the selected combination will be saved for each exposure time. If alternate gain option is selected, then the saved data in the first exposure time would correspond to Low Gain. In the second exposure time it would be the data corresponding to High Gain. The sequence goes on continuosuly for the entire observation period. The exposure time would be the same irrespective of whether it is low or high gain data in the sequence. The user will get data corresponding to only one gain at one exposure time unlike in the simultaneous gain option.
SUIT
What are the corrections done to create the level-1 data?
Bias removal using the overscan pixels. Gain correction and normalization for the four quadrants. Scatter light removal using the scatter model. For NB08, Ghost removal.
How to identify Flare and Non-Flare data?
The header ROI ID can be referred to identify flare and non-flare. 250 and 255 are reserved for Normal Flare (on-disk flare) and Prominence Flare (off-limb flare) respectively.
Can I use SunPy package?
Yes. The SUIT Image headers are configured for analysing using SunPy. The Map functionality will work perfectly well with SUIT FITS files.
Can I use SSWIDL/SolarSoft package?
Yes. The SUIT Image headers are configured for analysing using SSW.
What Image viewers are suitable for SUIT images?
SUIT images are configured for jhelioviewer and DS9. WCS formalism will work in both the softwares.
What is the Flare mode observation?
SUIT has on-board intelligence to detect flares. When this mode is turned on, the software will look for flare events and observes the same in ROI mode.
Why is the sun disk seen shifted to a corner in most of the SUIT images?
This is due to satellite orientation to align the VELC centre with the Sun Centre.
SoLEXS
What is the energy range of SoLEXS?
SoLEXS provides Soft X-ray sun-as-a-star spectra from 2keV to 22keV.
What are Solar Flares?
Solar flares are sudden increase in the flux and the increase can be as high as 5-6 orders of magnitudes in soft X-ray band. They occur in active regions (the dark regions seen in the visible band at the solar photosphere) and are most often accompanied by coronal mass ejections (CMEs).
What can be studied using X-ray spectra of Solar flares?
The soft X-ray spectra can provide both the thermal and non-thermal energy in the solar flares. By appropriate modeling of the soft X-ray spectra, the total energy content (thermal and non-thermal) can be obtained.
How is SoLEXS different from GOES and RHESSI?
SoLEXS provides soft X-ray spectra with a spectral resolution of about 170eV @6keV while GOES provides the flux in two X-ray energy bands and RHESSI provides X-ray spectra above 3keV but with coarser spectral resolution. RHESSI can do source localization but SoLEXS and GOES cannot.
How does SoLEXS complement other payloads on-board Aditya-L1?
SoLEXS in combination with VELC can provide CME-flare studies. SoLEXS in combination with SUIT can provide Flare driven prominence eruption studies and also bring out the spectral dependent solar flare energy (Spectral Energy Distribution of Solar flares in UV and X-ray bands). SoLEXS in combination with HEL1OS can provide a comprehensive solar flare spectra, similar to that of RHESSI but limited to 200keV. SoLEXS in combination with in-situ payloads can study the flare driven SEPs and their magnetic content.
HEL1OS
What is the pronunciaton of HEL1OS?
HEL1OS is pronounced as: hē′lē os′, that is, hee·lee·os.
What are the specifications of HEL1OS?
For the specifications and other technical details of HEL1OS, one should refer to the chapter on HEL1OS in the Aditya-L1 User Handbook (Refer 'OtherDownloads' section).
What are the modes of operation of HEL1OS?
HEL1OS always operates in Event mode.
Can one propose observations with HEL1OS on the Aditya-L1 Proposal Processing System?
The Operations of HEL1OS are not proposal driven. The payload is always operating in the Event mode with 100% duty cycle.
ASPEX
What is ASPEX?
ASPEX (Aditya Solar wind Particle EXperiment) is a scientific payload onboard the Aditya-L1 mission designed to study solar wind, suprathermal, and energetic particles in the interplanetary medium. It aims to understand the composition, origin, and acceleration mechanisms of these particles.
What are the components of ASPEX?
The ASPEX payload comprises two subsystems: the Solar Wind Ion Spectrometer (SWIS) and the Supra-Thermal and Energetic Particle Spectrometer (STEPS). Together, they span an energy range of 100 eV to 6 MeV/n, enabling the measurement and analysis of protons and alpha particles in the interplanetary medium.
How to access ASPEX data?
The Indian Space Science Data Centre (ISSDC) is the nodal agency for archiving and disseminating ASPEX data. Users can access data through the PRADAN interface, after registering. Detailed guidelines on data access and terms of use are available on the site.
How to read ASPEX data files?
Since all files are in CDF format, all metadata information is stored in the file itself. Moreover the files can be read from CDF tools available on NASA’s.
How to contact the ASPEX team?
For comments, suggestions, or inquiries, please reach out to the ASPEX team at aspexpoc@prl.res.in.
ASPEX-SWIS
What does the SWIS subsystem of ASPEX do?
The SWIS subsystem of ASPEX is a low-energy particle spectrometer designed to measure protons and alpha particles in the energy range of 100 eV to 20 keV. It employs an electrostatic analyzer coupled with a large-area microchannel plate (MCP) imaging detector for particle detection. SWIS includes two Top Hat Analyzers (THA-1 and THA-2) to sample particles from the ecliptic plane and those perpendicular to it, providing a 360-degree coverage in each plane.
What is the format of SWIS data?
SWIS instrument gives direction differentiated flux for proton and alpha particles and bulk parameters like number density, bulk velocity and temperatures. All the data products are written in CDF format (https://cdf.gsfc.nasa.gov/).
What is the cadence of SWIS data?
Nominally, SWIS provides flux values at a cadence of 5 sec for 50 energy steps, however, this may change depending on the current proposal. SWIS has provisions to limit energy step values and step numbers to perform faster scans.
What are level 1 and level 2 datasets?
Data level definitions are available in the user manual. Level 1 data is reorganised raw data as received from the onboard observations. Level 1 data is suitably processed to give level 2 datasets which are science ready.
ASPEX-STEPS
What does the STEPS subsystem of ASPEX do?
The STEPS subsystem of ASPEX is a high-energy particle spectrometer that measures protons and alpha particles in the energy range of 20 keV to 6 MeV/n. It consists of six detector units, each oriented in different directions to sample particles from various regions: Sun Radial (SR), Parker Spiral (PS), Earth Pointing (EP), Intermediate (IM) between SR and PS, North of the Ecliptic plane (NP), and South of the Ecliptic plane (SP). STEPS utilizes customized Si-PIN detectors for its measurements.
What type of data, STEPS give?
STEPS instrument gives direction differentiated flux. All the data products are written in CDF format (https://cdf.gsfc.nasa.gov/). It is to be noted that, during the nominal orientation of spacecraft, SR and SP detector data shows saturation likely due to light leakage issue, making it not suitable for scientific analysis.
What is the cadence of STEPS data?
STEPS gives data at a cadence of 10 mins.
What are level 1 and level 2 datasets?
Data level definitions are available in the user manual. Level 1 data is reorganised raw data as received from the onboard observations. Level 1 data is suitably processed to give level 2 datasets which are science ready.
PAPA
What is PAPA payload?
PAPA stands for Plasma Analyser Package for Aditya. The main scientific objective of PAPA is to study the solar wind (both ions and electrons).
How many sensors does PAPA payload have?
PAPA has two sensors; Solar Wind Electron Energy Probe (SWEEP) intended to measure the solar wind electron (energy and directional flux) and Solar Wind Ion Composition AnalyseR (SWICAR) having two modes of operation - ion mode where ion parameters (energy, directional flux and composition ) are measured and electron mode where electron parameters(energy, directional flux and composition ) are measured. These two modes in SWICAR are mutually exclusive.
What is the energy range for SWEEP and SWICAR sensors?
The energy range for SWEEP as well as SWICAR electron mode is 0.01-3 keV. The energy range for SWICAR ion mode is 0.01-25 keV.
What is the Field Of View (FOV) for SWEEP and SWICAR sensors?
SWEEP and SWICAR sensors are inclined perpendicular to each other. SWEEP scans 124° in elevation and with fixed 20° in azimuth in 32 angular bins with each pixel having FOV of 20° (azimuth)X 4°(elevation). SWICAR sensor scans 124° in azimuthal plane with fixed 20° in elevation in 32 angular bins with each pixel having FOV of 4° (azimuth)X 20° (elevation) for both ion and electron mode.
What is mass range for SWICAR ion mode?
SWICAR ion mode measures solar wind ions in the mass range of 1-60 amu.
What are the Level-1 products of PAPA payload?
The Level-1 products of PAPA will be count rates. For SWEEP and SWICAR electron mode at a given time there will be 16 × 32 count rates corresponding to 16 energy bins and 32 direction bins. For SWICAR ion mode at a given time there will be 32 × 32 count rates corresponding to 32 energy bins and 32 direction bins.
What are the Level-2 products of PAPA payload?
Level-2 products of PAPA payload will be differential fluxes. For SWEEP and SWICAR electron mode at a given time there will be 16 × 32 differential flux values corresponding to 16 energy bins and 32 direction bins. For SWICAR ion mode at a given time there will be 32 × 32 differential flux values corresponding to 32 energy bins and 32 direction bins.
PAPA Level-1 & 2 data products are available in which format?
PAPA Level-1 & 2 data products are available in Common Data Format (CDF). A detailed description about CDF format and package required to open the CDF files is available at “https://cdf.gsfc.nasa.gov”.
How to identify the PAPA SWEEP, SWICAR ion and SWICAR electron mode data products?
SWEEP data can be identified by the unique string ‘SWP_ele’ in the file name and similarly for SWICAR ion the string is ‘SWR_ion’ and for SWICAR electron it is ‘SWR_ele’.
How to identify Level-1 and Level-2 data products?
The file name contains the string ‘L1’ for Level-1 products and ‘L2’ for Level-2 products.
MAGNETOMETER
What is the purpose of the magnetometer instrument onboard Aditya-L1?
Magnetometer is an in-situ instrument that measures the local magnetic field vector. It provides a measure of the interplanetary magnetic field at the Sun-Earth L1 point. It is used by heliophysicsts to understand the effect of solar plasma and magnetic field output on the Earth’s magnetosphere.
What type of sensor is present in the magnetometer?
The sensor is a tri-axial fluxgate magnetometer that independently measures the magnetic components in three orthogonal directions using three separate sensing coils.
Why are there two magnetometers onboard Aditya-L1?
It is common practice to mount more than one magnetometer sensor on space missions. The spacecraft, being an electromagnetically active body, emits its own DC and AC magnetic fields. To separate out the contribution of spacecraft field from the measurement, multiple sensors are mounted (in this case it is two) at different distances from the spacecraft. This is achieved by considering that the effect of spacecraft field varies with sensors' distance, whereas the ambient field does not.
What is the cadence of magnetometer L1 data?
At level 1, the data product has a fixed cadence of 0.128 s.
What are the modes of operation for the instrument?
There are four different ranges of operation for the magnetometer. They are +/- 60000 nT, 10000 nT, 5000 nT, and 256 nT. Different range facilitate measurement in different ambient conditions. For ground testing, to account for the Earth’s magnetic field the range selected is 60000 nT. For the IMF measurement at L1, the default mode is 256 nT. This is now fixed and shall continue to be so for the rest of the Mission.
What is the cadence of magnetometer L2 data?
At level 2, the data product has a minimum cadence of 10 seconds. It is to be noted that the L2 data is averaged data (for a given 10-second duration) and not sub-sampled L1 data. If a user needs to use higher cadence data, they need to use L1 data.
What is data format for magnetometer data?
The data is formatted into netCDF (Network Common Data Form) files at both L1 and L2. It is a standard scientific data format which is self-describing and machine-independent. Other contemporary international magnetometer instruments also use either CDF or netCDF formats.
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 SPICE data organized?
The dataset contains spice kernels for the ephemeris and attitude information of the Aditya-L1 spacecraft along with clock kernels and other generic kernels. We are providing 2 kinds of CK/SPK files. For the current month, we provide a daily updating SPK/CK file which will have our ephemeris/attitude based on our current best knowledge but which may improve in future. These files are available in Other-Downloads area and not in SPICE area. Once we have the best information possible, the optimal monthly file for that month is available in the SPICE area. So, the SPICE area will have all previous month files(and not the current month). These are uploaded as monthly files. XML label files are also provided