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Mission
Jason-1 is an altimetric mission that measures significant wave height, mean sea surface, sigma0 (which can be converted to wind speed), and all the parameters needed to calculate sea surface height anomalies. It launched December 7, 2001 and began collecting data January 15, 2002 ( cycle 1). As of December 2007, Jason-1 has an orbit accuracy of ~2.5 cm and measures sea surface height with an accuracy of ~3.9 cm. A list of the Jason-1 cycles by date is available at: http://podaac.jpl.nasa.gov/DATA_CATALOG/j1_cyclelist.txt |
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Sea Surface Height Anomalies during October
based on 6 years of Jason-1 Data (2002-2007).
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ANNOUNCEMENTS |
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- Jason-1 nominal operation: Jason-1 returned to normal function August 20, 2008 at 10:57 UTC. |
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- I/GDR-c Coming Soon! |
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JASON-1 Table
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FTP / HEFT |
s/w |
4-6 weeks |
x |
calc |
x |
Documentation:
User Manual / Abstract / References |
Comments: |
Most accurate and detailed product from Jason-1. Does not include SSHA, but this parameter can be calculated per the instructions in the Handbook. |
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FTP / HEFT |
s/w |
6 weeks |
x |
x |
x |
Documentation:
User Manual / Abstract / References
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Comments: |
SSHA derived from the GDR product.
Data was adjusted to exclude values flagged in the GDR. |
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6 weeks |
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x |
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Documentation:
User Manual / Abstract / References |
Comments: |
An along track gridded version of the SSHA |
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2-3 days |
x |
calc |
x |
Documentation:
User Manual / Abstract / References
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Comments: |
Similar to GDR. However, data are obtained in near real time and contain fewer corrections. Therefore, this product is less accurate than the GDR and should only be used if the GDR file is not yet available. |
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2-3 hr |
x |
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Documentation:
User Manual / Abstract / References |
Comments: |
Near real time data intended for meteorological use. This product has the fewest corrections of the Jason-1 products. |
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Announcements
Jason-1 nominal operation:
Jason-1 returned to normal function August 20, 2008 at 10:57 UTC and started collecting data at 11:00 UTC from a safehold that started August 14, 2008 08:51 UTC. Due to this safehold and the previous one, very little scientific data was collected during cycle 243. More information on the start and end dates of the safeholds can be found at http://podaac.jpl.nasa.gov/DATA_CATALOG/j1_safehold.txt.
Jason-1 I/GDR-c will be released soon.
Starting with IGDR cycle 237 pass 121 only version c will be distributed and b will be discontinued. Cycle 233 will be the first GDR-c available. Cycles 1-232 will be reprocessed to provide a consistent data set. Version c has an improved orbit, altimeter corrections, radiometer parameters, dry troposphere corrections, ocean tides, and rain and ice flags. It also contains 2 new parameters, mean dynamic topography (mdt) and pseudo altimeter datation bias correction (pseudo_datation_bias_corr_ku). Updated documentation will be available soon.
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Temporal Resolution
It takes approximately 10 days for Jason-1 to complete a cycle that surveys the entire Earth. Each cycle consists of 254 passes, which is half an orbit around the Earth and contains ~56 minutes of data. There is ~1 second between measurements.
Spatial resolution
Jason-1 surveys from 66.15° to -66.15°. The along track resolution is 0.0001° in latitude and 0.05° in longitude. A table showing the equator crossing for each pass is available at: ftp://podaac.jpl.nasa.gov/pub/sea_surface_height/jason/gdr/doc/
Handbook_Jason_v3-0.pdf |
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Documentation
Jason-1 Mission:
http://topex-www.jpl.nasa.gov/mission/jason-1.html
Picot, N., K. Case, S. Desai and P. Vincent, 2006, “AVISO and PODAAC User Handbook.
IGDR and GDR Jason Products”, SMM-MU-M5-OP-13184-CN (AVISO), JPL D-21352 (PODAAC). ftp://podaac.jpl.nasa.gov/pub/sea_surface_height/jason/gdr/doc/Handbook_Jason_v3-0.pdf Berwin, Robert. W, "PO.DAAC Jason-1 Sea Surface Height Anomaly Product User's Reference Manual"
ftp://podaac.jpl.nasa.gov/pub/sea_surface_height/jason/j1_ssha/doc/j1ssha_manual_v2.html Berwin, Robert. W. "PO.DAAC Along-Track Gridded Sea Surface Height Anomaly for TOPEX/Poseidon and Jason-1, User's Reference Manual" ftp://podaac.jpl.nasa.gov/pub/sea_surface_height/jason/j1_atg/doc/along_track_gridded_manual_v2.html
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Known Problems and Issues
There are times when the JASON-1 satellite entered safehold-mode, and no data was collected as a result. A list of safing events is available at http://podaac.jpl.nasa.gov/DATA_CATALOG/j1_safehold.txt
The satellite also performed a series of maneuvers to ensure orbital accuracy. A list of maneuvers is available at http://podaac.jpl.nasa.gov/DATA_CATALOG /j1_maneuver.txt Various conditions, such as heavy rain or ice, may affect input titleimetric measurements. Known environmental and geophysical problems are flagged to allow researchers to easily evaluate these measurements. A description of the Jason-1 flags is available in the Jason-1 IGDR and GDR. ftp://podaac.jpl.nasa.gov/pub/sea_surface_height/jason/gdr/doc/Handbook_Jason_v3-0.pdf |
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Frequently Asked Questions
http://podaac.jpl.nasa.gov/FAQ/index.html#altimetry
Q: What are the differences between Jason-1 GDR-b and GDR-c?
A: The GDR-c has a different file naming convention and has improved corrections.
- The file extension .NASA and .CNES are not added to the GDR-c file names
- There are two new parameters, pseudo_datation_bias_corr_ku and mdt
- Better orbit, sea stat bias, ionospheric range, inverse barometer, and tidal corrections
- Improved rain and ice flags
For more details please refer to the handbook.
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Citations/References
Menard, Y. and B. Haines, 2001. “Jason-1 CALVAL Plan”, JPL Ref: TP2-J0-PL-974-CN (PO.DAAC).
http://podaac.jpl.nasa.gov/jason/documents/calval4.0.pdf Vincent, P., M.Ablain, J.Donrandeu, S.Desai, and K.Case. “Jason-1 Calval results”.
http://www.jason.oceanobs.com/html/kiosque/newsletter/news10/vincent_uk.html Chambers, D.P., J. C. Roes, T.J. Urban. 2003. Calibration and verification of Jason-1 using along-track residual with TOPEX. Marine Geodesy. Vol. 26, no. 3-4, pg. 305-317. MacMillan, D., Y. Bock, P. Fang, B. Beckely, C. Ma. Calibration of the TOPEX and Jason-1 Altimeter microwave radiometers using VLBI and GPS derived tropospheric delays. http://sealevel.jpl.nasa.gov/science/invest-macmillan.html
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