This document presents guidelines for formatting HDF-EOS files for NASA's Aura satellite mission, which is scheduled to launch in June 2003. It summarizes the Aura instruments, discusses changes from previous guidelines, and outlines the standardized structure for HDF-EOS files, including dimensions, geolocation fields, data fields, and attributes. The guidelines are intended to promote cross-platform use and understanding of Aura data files.

1. HDF-EOS Aura File Format Guidelines
HDF-EOS Aura File Format
Guidelines
Cheryl Craig
February 26, 2002
Cheryl Craig
HDF-EOS Workshop V
Feb 26, 2002
1

2. HDF-EOS Aura File Format Guidelines
What Is Aura?
• Third in series of EOS atmospheric chemistry
satellites (1:45 PM equator crossing time)
• Formerly known as CHEM
• Scheduled launch date of June 2003
• Level 2 data products include:
– Vertical profiles of temperature, pressure, chemical
and aerosol species
– Column amounts of chemical species
– Cloud properties
Cheryl Craig
HDF-EOS Workshop V
Feb 26, 2002
2

3. HDF-EOS Aura File Format Guidelines
Aura Instruments
• HIRDLS (High Resolution Dynamics Limb Sounder)
– Limb infrared sounder
– University of CO and Oxford
• MLS (Microwave Limb Sounder)
– Limb microwave sounder
– JPL
• OMI (Ozone Monitoring Instrument)
– Nadir wide-field-imaging spectrometer
– Netherlands, Finland and US
• TES (Tropospheric Emission Spectrometer)
– Nadir and limb infrared-imaging spectrometer
– JPL
All instruments have world-wide co-investigators
Cheryl Craig
HDF-EOS Workshop V
Feb 26, 2002
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4. HDF-EOS Aura File Format Guidelines
Why Guidelines for Aura Instruments?
• HDF-EOS Swath allows a lot of flexibility
• Ease cross-platform use of Aura files
– Ease development of software
– Easier to understand
• Intended to standardize Level 2 files
(may apply to Level 3 and above as well)
Cheryl Craig
HDF-EOS Workshop V
Feb 26, 2002
4

5. HDF-EOS Aura File Format Guidelines
Changes Since HDF-EOS Workshop IV
* Adopted HDF-EOS5 as at-launch version
* One type of data file organization now –
MLS will use HDF-EOS5 links capability
for L2gpValue
* Swath Name – instrument specific
* Pressure is stored in geolocation field and
swath attribute (duplicate copy)
* New Item
Cheryl Craig
HDF-EOS Workshop V
Feb 26, 2002
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6. HDF-EOS Aura File Format Guidelines
*
*
*
*
Changes Since HDF-EOS Workshop IV
(continued)
Three levels of attributes (file, swath and
data field)
Attributes are now suggested, but not
mandatory (except for Pressure)
Instrument teams modified Geolocation
and Data Field valids and units
Added appendix of pre-HDF-EOS5 file
formats
Cheryl Craig
HDF-EOS Workshop V
Feb 26, 2002
6

7. HDF-EOS Aura File Format Guidelines
Guidelines List
* Instrument teams will use HDF-EOS5 by
launch
• Aura Level 2 files will use HDF-EOS Swath
• HDF-EOS structure names will strictly adhere
to Valids list
• Data will be reported on a pressure grid and be
ordered from ground to space
Cheryl Craig
HDF-EOS Workshop V
Feb 26, 2002
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8. HDF-EOS Aura File Format Guidelines
Guidelines List (continued)
• Data fields will be ordered with pressure
coordinate being the fastest incrementing
coordinate
• Data fields will be in units specified
• HDF fill value and MissingValue will have the
same value
• Instrument geolocation fields unique to
particular instrument will be prefixed with
instrument name
Cheryl Craig
HDF-EOS Workshop V
Feb 26, 2002
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9. HDF-EOS Aura File Format Guidelines
Organization of Data Fields and Attributes
Swathname: Instrument Specific
Dimensions:
nTimes
nLevels etc.
Each file may have
one or more swaths
Geolocation Fields:
Time
Latitude etc.
Data Fields:
Temperature
O3 etc.
Each swath may
contain one or more
species
Global Attributes:
Instrument Name
Process Level etc.
Cheryl Craig
HDF-EOS Workshop V
Feb 26, 2002
9

10. HDF-EOS Aura File Format Guidelines
Standard Names
•
•
•
*
*
•
Adhere to strict names (spacing and capitalization
required)
Dimension names (nTimes, nLevels, nWavel, nXtrack)
Geolocation Fields – Used to hold descriptor data
(includes SolarZenithAngle, OrbitAscendingFlag, etc.)
Data Fields – Contains measured and derived data
File Attributes (HDF-EOS Global File Attributes) –
Includes InstrumentName, ProcessLevel, etc.
Swath Attributes (HDF-EOS Group Attributes) –
Pressure and VerticalCoordinate
Data Field Attributes (HDF-EOS Local Attributes)
–Includes MissingValue, ScaleFactor, Units, etc.
Cheryl Craig
HDF-EOS Workshop V
Feb 26, 2002
10

11. HDF-EOS Aura File Format Guidelines
Conclusions
• Initial standardization complete and adopted
by all instrument teams
• Revisions are adopted as agreed upon by the
authors, who represent every instrument team
• Standard may continue to evolve as instrument
teams get better understanding of their data
storage needs
• URL of document:
http://www.eos.ucar.edu/hirdls/HDFEOS_Aura_File_Format_Guidelines.pdf
Cheryl Craig
HDF-EOS Workshop V
Feb 26, 2002
11