Subject: NOAA-15, 16, & 17, All Instruments, Implementation of Level 1B Format Changes - Update, Implementation Date 27 April - Issued: 120 April 2005, 2100 UTC
Implementation of Level 1B Format Changes - Update
Date/Time(UTC) Message Issued:
20 April 2005, 2100 UTC
NOAA-15, 16, 17
Date/Time(UTC) of Initial Implementation:
27 April 2005, TBD UTC
Details/Specifics of Change:
The implementation of the new level 1B format has been rescheduled for
Wednesday, April 27th. In working with the HIRS instrument scientist and
the National Weather Service, we have accounted for additional anomalies
seen in the NOAA-15 HIRS data. We have updated the user format
documentation to help you better understand and apply the calibration
anomaly flags. The new/updated flags should have no impact on users
even if you are using the old software, unless you are always checking
the channel flags regardless of what the scanline flag, bit 6,
Updated format documentation is found on our anonymous ftp site:
in the file named HIRS1bFormat.doc.
A separate email will be sent when the test data is available.
The new HIRS 4.0 algorithm improves the calibration accuracy when the
instrument filter temperature is changing rapidly, as is often the case
for NOAA-15 and occasionally for NOAA-16 and 17. During normal
operations, the difference in the radiances produced by the two
algorithms is very small (within noise spec.).
Below is information to help you in determining if a change is needed in
your HIRS software.
1. Calibration Quality Flags (channel flags in bytes 37 through 76)- The
order of the flags between the operational version and the new
version are different (they are set based on the same specification).
The operational version has them stored in the wrong order. It has the
flags stored in channel sequential order. The KLM documentation states
that these flags are stored in the same order as the telemetry (Channels
1, 17, 2, 3, 13, 4, 18, 11, 19, 7, 8, 20, 10, 14, 6, 5, 15, 12, 16, 9 ).
On March 11, 2005, the parallel test data were modified to report the
flags in telemetry order in the level 1B.
2. Quality Indicator Bit Field - "Bit 28: insufficient data for
calibration (see below)" - is not changed, but corrected to match the
description. Users should follow the direction to check the additional
flags indicated in the document.
3. Scan Line Quality Flags [Calibration Problem Code] - "bit 6:
anomalous space or BB view data, calibration slope value came from the
HCF, or some QC tests could not be applied in some of the IR channels" -
The definition is changed but the function is the same as that of the
4. Calibration Quality Flags -
bit 5: calibration failed
bit 4: anomalous space or BB view data
bit 3: calibration slope value came from the HCF
bit 2: BB views failed NEDC test
bit 1: space views failed NEDC test
bit 0: some QC tests could not be applied
These channel flag definitions were made practical and have no major
impact on users unless they are checked regardless of bit 6 value above.
"bit 4: anomalous space or BB view data" is a summary of bits 0 and 3.
We have found that bits 1 and 2 reflect when data exceeds instrument
specification, however, most of time the data is still useful and causes
the user to throw away good data. We are suggesting that you follow this
sequence when checking the channel bits:
If "bit 6" = 0 then continue processing
If "bit 6" not = 0 then check the channel flags (ch_flag)
If "ch_flag" = 0 then continue processing
If "ch_flag" > 6 then follow your normal problem path (checks bits 3 - 5)
Please contact us if you have questions or concerns.
Contact Person(s) Name/Email/Phone Number for Questions:
Changyong Cao email@example.com 301-763-8136 ext. 196, instrument
Emily Harrod firstname.lastname@example.org 301-452-5247 ext 117, operations support
Web site(s) that contain other relevant information (where applicable):
http://www.osdpd.noaa.gov/PSB/PPP/PPP.html - History of level 1B
http://www.ssd.noaa.gov/PS/SATS/messages.html - All user notices
http://www.oso.noaa.gov/poesstatus/ - SOCC polar satellites status
http://www.oso.noaa.gov/daily-news/index.htm - SOCC morning reports
* Emily D. Harrod
* Computer Operations Branch
* Pre-Product Processing Group
* E/SP11, Federal Building #4, room 0318
* 5200 Auth Road
* Suitland, Maryland 20746-4304
* voice 301-457-5247 ext 117
* fax 301-457-5199
* email Emily.Harrod@noaa.gov