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Introduction

This short document is intended to get a new user familiar with selecting downloading and viewing NOMAD data. It is intended to be a living document so any feedback or ideas on how to improve it will be useful.

NOMAD Files

A full description is available in the EAICD section 4:

Raw

This is how a NOMAD raw filename appears:

  • nmd_raw_sc_so_20200304t092012-20200304t093528-22-10168-1

This example is a raw SO science product with the start and end time in UTC indicated. Here the instrument specific information is:

  • 22: NOMAD Packet Type number (see EAICD section 2.6.3.1)
  • 10168: Orbit Number
  • 1: Observation Number

Calibrated

For solar occultation observations with SO or LNO: 

  • nmd_cal_sc_<channel>_<YYYYMMDD1>T<hhmmss1>-<YYYYMMDD2>T<hhmmss2>-<altitude_type>-<obs_type>-<diffraction_order> 

For nadir observations with LNO: 

  • nmd_cal_sc_lno_<YYYYMMDD1>T<hhmmss1>-<YYYYMMDD2>T<hhmmss2>-<obs_number>-<obs_type>-<diffraction_order> 

For UVIS observations: 

  • nmd_cal_sc_uvis_<YYYYMMDD1>T<hhmmss1>-<YYYYMMDD2>T<hhmmss2>-<obs_type> 

Where: 

  • <channel> is “so” for the SO channel science data, “lno” for LNO data, or “uvis” for UVIS data. 
  • <YYYYMMDD1>T<hhmmss1> is the observation start time in years, months, days, hours, minutes and seconds respectively. 
  • <YYYYMMDD2>T<hhmmss2> is the observation end time in years, months, days, hours, minutes and seconds respectively.
  • <altitude_type> denotes whether the given diffraction order was measured continuously throughout the occultation, or if it was switched at 50km. The three options are: H=measured only at high altitudes; L=measured only at low altitudes; and A=measured at all altitudes. The latter is by far the most common. 
  • <obs_number> is a special flag for LNO, as it is theoretically possible that each nadir observation can be split into two halves, with a different set of diffraction orders used for each half. The number will be set to 1 for diffraction orders measured during the entire or first half of the nadir; or will be set to 2 for those measured during the second half of the nadir observation. At the time of writing this splitting has never been used, so only values of 1 will be present in the archive. 
  • <obs_type> is the observation type, e.g. I=occultation ingress, E=occultation egress, etc (see below). 
  • <diffraction_order> is the observed SO/LNO diffraction order, in the range 90-225, if appropriate. 

Observation Types:

  • I = Ingress
  • E = Egress
  • G = Grazing Occultation
  • S = Fullscan (during a solar occultation observation) 

  • F = Fullscan (during a nadir observation). 

  • D = Day nadir

  • N = Night nadir

  • L = Dayside limb observation

  • O = Nightside limb observation 

  • C = Calibration 

More information on observation types can fe found in the NOMAD EAICD section 2.8 and on diffraction orders in section 2.7.

How To Navigate the PSA

The easiest way to get started is to go to psa.esa.int and in the welcome/home screen start typing NOMAD and select "NOMAD (Instrument)".

This will take you to the PSA table view which will show all NOMAD data. This view has a filter menu on the left allowing you to select further.

Note you will not see browse images on the latest data files which are displayed at the top because browse images are only displayed after the 6 month proprietary period. Also browse images are only available for calibrated data so for most data on this initial view the browse images are Not Available.

If you don't want to look at the Housekeeping (HK) and SINBAD files you can uncheck these in the filter menu and re-do the search using the button at the bottom of the filter menu.

Using this filter menu, you can also choose to look at only calibrated data after expanding the "Processing Level" menu, a time range, and/or all versions. By default only the most recent product versions are displayed.

Once you have made selections in the filter menu you will need to initiate another search using the button at the bottom of the menu as results are not updated on the fly.

Using Advanced Search

Currently there is no toggle to select by observation type but advanced search can be used for this. Fr example to only list egress observations you can enter:

  • logical_identifier like '%-e%'

additionally for a particular order:

  • logical_identifier like '%-e-190%' or
  • logical_identifier like '%-e%190%'

Downloading Data

There are two ways of downloading data either directly or via the download manager. For both methods products need to be selected first using the tick boxes in the table. Note the 'select all' button only selects all products on the page being viewed so to download multiple pages the select all needs to be checked on each.

Once the data are selected the download button on the top right of the screen will then create a popup with the option of 'Download' or 'Send to Download Manager'. If the latter is chosen the number of products selected are shown as in a blue rectangle above the download view button on the top left. Clicking outside the popup will dismiss it. Using the download manager you can additionally select calibration files and documents for your download.

FTP

For large downloads the PSA also offers an FTP server at: 

Here the data are organised by data_level collection, mission phase, subinstrument, orbit range and orbit.

How to View and Start Interacting with the Data

The easiest way to view the NOMAD data is to use the PDS4 viewer from the Small Bodies Node. This can be downloaded from 

Not all operating systems are yet supported so instead you can use the Python tools which form part of the viewer back end to read in and display the data manually. The tools can be found at

Where to Find Out More

A detailed description of the NOMAD data and how it is produced is in the EAICD. The EAICD can be downloaded from the PSA GUI using the download manager or it can be accessed directly from ftp using

The latest version of the detailed user manual for the PSA can be downloaded from:

More about the NOMAD Instrument can be found at:

If further help is required please contact the PSA Helpdesk (psahelp@rssd.esa.int) or Tanya Lim (tlim@sciops.esa.int).



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