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[PR data loss and recovery]

Dec 18, 2009

TRMM PR product release after PR B-side

TRMM/PR suffered a lose of its original (A-side) electronics interface. Fortunately JAXA/NICT had designed and built the TRMM PR with redundancy (B-side). On May 29, the A-side began to be a problem and the process of switching to the B-side electronics was begun. This changeover including investigation took about 2 weeks.

NASA/PPS have been operating PR with the B-side since June 17. B-side electronics have slightly different characteristics than the A-side and JAXA has been carefully investigating the best way to calibrate the PR so as to maintain continuity with the A-side driven measurements. This has required not only internal calibration information but also several external calibrations. It has also required looking at a longer period of data using B-side to ensure it is fully understood. These re-calibration of B-side took about 5 months.

On December 18, JAXA and PPS are pleased to inform you the PR B-side all standard products release from June 19.


Please also be aware of the following issue for TRMM PR Level 3 products after TRMM PR switched to the B-side: The PR anomaly has caused the loss of PR data from 29 May 2009 to 19 June 2009. As a result, the June 2009 Level 3 PR products contain only 12 days of data. This makes the June 2009 products less reliable due to the lack of sufficient data upon which to base the statistics. Please take care when using the June 2009 product for quantitative analysis.

Oct 16, 2009 After an instrument anomaly on May 29, 2009 the TRMM PR resumed observations on June 17th, 2009. All TRMM PR production data is currently being held until a calibration effort is completed by JAXA.

The recalibration effort by JAXA has required internal and external calibrations utilizing the ground-based Active Radar Calibrator. The impact of the new calibration curve on the rain retrievals is being examined by JAXA and the PR Team. Particular attention is being given to any biases introduced and changes in noise levels that impact sensitivity to ensure that continuity of the retrievals can be preserved on either side of the anomaly date

The TRMM PR is still recording observations which the ground system is receiving, all PR housekeeping indicate the radar is operating normally and the instrument is in good condition. Users can expect the only permanent gap in TRMM PR data due to this anomaly to start on May 29, 2009 and last through June 17-19, 2009. The exact dates and orbit numbers will be designated by JAXA.

JAXA will be briefing the Joint Precipitation Science Team at the upcoming PMM meeting in Utah at the end of October, 2009. Be assured that JAXA, the PR Team and NASA are working to get high quality rain retrievals out to all users as soon as possible.

June 18, 2009 On May 29, 2009, the TRMM PR experienced a major anomaly, resulting in a loss of data. JAXA and NASA have inferred that a frequency converter and interface system unit might not have worked normally. JAXA and NASA successfully switched those two units to the backup systems on June 17, and the PR became operational again. Note that this change could have some impact on the data. JAXA and NASA are going to examine the data over the next month or more to identify the influence, if any.

PR data delivery has stopped since May 29th, and will stay halted during the period above.

June 5, 2009 On 5/29 at UTC 04:39:49 the TRMM PR experienced a data loss
that has continued through the latest realtime pass.
Currently, we are investigating the cause of the data loss.
TMI and VIRS have no trouble to process the realtime data.

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