Oxford MIPAS meeting#120
19 Jun 07

Present

Oxford: Anu Dudhia, Jane Hurley, Luis Millan-Valle, Joanne Walker, Claire Waymark
RAL: Alison Waterfall

Since passive decontamination MIPAS has performed a standard 10-day cycle of MA/NOM mode observations and is about to perform some UA/MA mode measurements for the summer solstice.

Mission Planning Document for 2007 [XLS] [HTML].
Currently defined measurement modes
Envisat Web-Site

May Monthly Report (AD) [Prev] [Next]

Full report obtainable from http://earth.esa.int/pcs/envisat/mipas/reports/monthly/

Summary below.

Anomalous Scanning (AD) [Prev] [Next]

Now listed as a L1 anomaly in the May Report (section 3.5.8)

Problem was connected with the Orbit Control Manoeuvre 1-3 April - when MIPAS restarted it only had a partially complete set of scan tables.

NOy (JW) [Prev] [Next]

Previously compared monthly means of ESA L2 N2O and NOy species (N2O, NO2, HNO3) to see if RR data are consistent with what was observed with FR data. - Some results presented at last week's QWG meeting (below)

Now looking at HNO3 v (night) NO2 - expect to see linear anticorrelation as a function of time of year (and solar illumination).

Cloud Detection (JH) [Prev] [Next]

Generated a set of singular vectors to characterise simulated cloud-free radiances, plus additional orthogonal vectors to characterise simulated cloud-contaminated radiances

Applying the vectors to real data
- Calculate chi-square statistic of residuals after fitting just clear vectors
- Similar statistic fitting both clear+cloudy vectors
- Take ratio of first/second statistic as measurement of cloudiness
Value=1 implies cloud free, >1 cloud contamination

Next: need to compare this method of cloud detection with other methods such as cloud-index and simple threshold radiance. Also need some method of determining which is 'best'.

Mesospheric Retrievals (LMV) [Prev] [Next]

Trying a linear least-squares fit retrieval for pT, O3 and H2O using entire MIPAS bands (screening out lines affected by non-LTE effects and contaminant gases).

Attempting to identify vibrational levels associated with high altitude CO2 features (perhaps to include fit of Vibrational Temperature as part of retrieval to cope with non-LTE effects)
Found a problem trying to fit H2O lines with simple linear model. It might be that most of these lines are saturated even in the lower mesosphere (this is known to cause problems for the ESA L2 H2O retrievals).

MIPAS/TES Retrievals (CW) [Prev] [Next]

Aim is to combine MIPAS limb measurements of stratospheric O3 with TES nadir-viewing measurements to obtain more information on tropospheric O3 profile (basically how TES was supposed to work before their problems with limb-views)

Microwindows selected for 2200cm-1 region were very noisy - these should not have been selected in the first place
Found a bug in code and the new selection produces microwindows for joint pT + H2O + O3 + surface temperature retrieval in 1000-1300cm-1 region [Plot]

Oxford L2 Processing (AD) [Prev] [Next]

Running MORSE retrieval to process L1B data for selected days throughout the full and reduced resolution dataset.

pT, H2O, O3, HNO3, CH4, N2O, NO2, CFC-11, CFC-12, ClONO2, N2O5 and CO (LTE assumption).

[List of processed days] - 47 days completed so far
1 day/month of full resolution data - only missing Feb 2004 now.
1 day/month of reduced resolution data from Jan05 onwards
NOM & MA mode data from January 2005 before/after SPE - completed
Now adding some days for Teresina campaign (June 2005) for comparison with ESA products.

RAL Work (AW) [Prev] [Next]

Investigating differences between RFM and FM2D (RAL model) for limb radiances in 950cm-1 region - might be a problem with H2O lines at low altitude.

MIPAS QWG-13 (AD/JW) [Prev] [Next]

Firenze, 12-14 June 2007.

[Minutes]

[Notes] from JW

Oxford Presentations

Pointing Retrieval (.ppt) (AD)
Radiometric Offset (.ppt) (AD)
L2 NOy comparisons (.pdf) (JW)

ACPD Papers [Prev] [Next]

Papers selected from the ACPD website for discussion

"The influence of cloud top variability from radar measurements on 3-D radiative transfer": F. Richter et al. (published 11.06.2007, open until 06.08.2007); Introduced by JH.
"First direct observation of the atmospheric CO2 year-to-year increase from space": M. Buchwitz et al. (published 16.05.2007, open until 11.07.2007); Comments being collected by CW.
"Geophysical validation of temperature retrieved by the ESA processor from MIPAS/ENVISAT atmospheric limb-emission measurements": M. Ridolfi et al. (published 25.04.2007, open until 20.06.2007); Comments being collected by LMV.
"Vertical profiles of lightning-produced NO2 enhancements in the upper troposphere observed by OSIRIS": C. Sioris et al. (published 11.04.2007, open until 06.06.2007); Now closed. Comments submitted by JW.

Other papers with 'MIPAS' in the title in the Open Discussion phase, which may be adopted at a future meeting

"Geophysical validation of MIPAS-ENVISAT operational ozone data": U. Cortesi et al. (published 07.05.2007, open until 02.07.2007)
"Validation of MIPAS HNO3 operational data": D. Y. Wang et al. (published 17.04.2007, open until 12.06.2007)

Summary of the May Monthly Report (F.Niro, ESRIN)

During May 2007 the MIPAS instrument performs really well, in fact only two INT anomalies occurred. However the instrument was off from the 2nd to the 4th of May as a consequence of a flight segment anomaly due to the upload of conflicting CTI tables. Furthermore from 29th May to the 6th of June the instrument was switched off in order to perform a passive decontamination (see 2.2.2).

The instrument planning for the reporting month is hereafter summarized (see 2.2.1):

The duty cycle was raised up to 60% as a consequence of the more stable instrument performance. A further increase up to 80% is planned for next month.
The baseline scenario was planned, it consists on the following sequence of measurements: 1 day MA + 3 days NOM + 2 days off + 2 days NOM + 2 days off
The pointing test planned for the 2nd of May were lost due to the instrument anomaly, they were planned again and acquired on 24th May. These tests were made changing the pitch harmonics and the pitch bias in the planning in order to investigate the instrument pointing

The availability of the instrument was slightly lower than the previous month (92 % of the planned time) owing to the flight segment anomaly occurred on 2nd May. The measurement segments not processed to level 0 due to failures at the ground segment were about 2% of the planned measurement time (see 2.2.4).

An anomaly was reported by A. Dudhia (OU), the problem is that an anomalous scan pattern was adopted in the period 3 – 11 April 2007. During this period the measured scan consisted of 22 sweeps with tangent heights from 101 to 37 Km at 6 Km steps, each tangent altitude was scanned twice. The investigation shows that the problem was due to a flight segment anomaly, in particular to the fact that not all the correct CTI tables were up-linked to the platform when the measurements started. All the measurements taken during this period are affected by this problem that will impact significantly the level 2 processing of these orbits (see 3.5.8).

An anomaly was detected during the daily monitoring of the level 1 products, the problem consists in a wrong radiometric calibration and it was due to the usage of a not correct auxiliary file. The affected products are going to be reprocessed at D-PAC, the list of reprocessed data will be provided to the QWG (see 3.5.7).

The monitoring of the instrument temperatures shows an increase of about 3K over the reporting month due to the seasonal variation of the instrument temperature (see 2.3.1).

The cooler performs well during this month; the vibrations were always below the warning level of 8 mg. However a significant increase of the compressor vibrations was observed in the last two months due to the seasonal increase of the instrument temperature. In particular by the end of the reporting month the compressor vibrations approach the warning level. The situation was resolved with the passive decontamination started on 29th May. This level of vibrations was considered by Astrium too risky for the cooler performances, therefore they recommended for the future to perform the passive decontamination always at the beginning of May (1st May) (see 2.3.3).

The long term trend of ADC max counts in channel A1 shows a strong correlation with the instrument self-emission and with the detector ice contamination. During the reporting month an increase of ADC max counts is observed linked to the seasonal variation (increase) of the instrument temperature (see 2.3.4).

The monitoring of the spectral correction factor shows a stable situation since the variations are of the order of 3 ppm over almost two years of operations, the observed variations are due to noise (see 2.4.2).

The gain weekly increase during the reporting month is nominal, the maximum of gain increase in all the MIPAS bands remains below the acceptance criterion of 1%/week (see 2.4.3.1).

The analysis of the accumulated gain shows a steady increase of the gain with a constant rate and highlights the decontamination events throughout the mission. During the last year we observed a decreasing slope of the gain curve, showing that the detector is more and more ice-free. However the slight degradation of the cooler performance observed during the reporting month produced an increase of the ice contamination with a consequent increase of gain factor. The situation was solved with the passive decontamination of 29th May (see 2.4.3.2).

The absolute mispointing error is stable around a value of -30mdeg. The seasonal variations of the pointing error are small and below the fixed threshold of 8mdeg (see 2.4.4).

The long term monitoring of fringe count errors (FCE) for the RR mission was investigated this month. A statistical approach was adopted and the results are reported in this report. This analysis shows that the width of the statistical distribution of the FCE can be used as a measure of the INT performances. In fact the long term variation of the FCE statistical dispersion is highly correlated with the number of IDU velocity errors (see 2.4.5.1).

The long term monitoring of the detected spikes is reported in this MR. The presence of spikes on the scene IGM is detected by the L1 processor, these spikes are corrected in order to avoid artefacts in the spectrum. The number of spikes in channels A1, A2, B1 and B2 is increasing up to Dec 2006, while since Jan 2007 we observe a decrease. The channels C and D (the detector most affected by spikes) didn’t show any trend so far (see 2.4.5.2).

The level 0 NRT daily reports can be accessed at the following address:
http://earth.esa.int/pcs/envisat/mipas/reports/daily/Level_0_NRT/
The level 1b OFL daily reports can be accessed at the following address:
http://earth.esa.int/pcs/envisat/mipas/reports/daily/Level_1_OFL/

Oxford MIPAS meeting#120 19 Jun 07

Summary of the May Monthly Report (F.Niro, ESRIN)

Oxford MIPAS meeting#120
19 Jun 07