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Update chla_mission_execution.md #43

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27 changes: 22 additions & 5 deletions sections/chla_mission_execution.md
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Expand Up @@ -4,21 +4,38 @@
This section covers the activities of those deploying and recovering the gliders in the field in addition to best practices for glider pilots.

## Deployment
...
While keeping the oxygen sensor protected from sunlight and kept moist, any lens cover must be removed prior to deployment. The use of highly visible material, such as a red flag, can aid in ensuring its removal in addition to the pre-deployment checklist.

In-air measurements prior to deployment can and should be carried out together with the in-situ air pressure and relative humidity measurements to provide an additional reference for calibration. Details of this procedure can be found in the in-air calibration section.

## In-situ reference samples
...
Even with good ballasting it can require several dives for a glider to fly correctly with an ideal dive profile.
Reference data should therefore only be performed after the glider is flying well, and ideally as close to the glider’s last known position as possible.
Ideally multiple sets of samples should be taken unless the horizontal variability of the deployment region is very well characterized.
This requires coordination between the deployment team and the glider pilot and should be part of the mission planning.

(deployment_small_boat)=
## In situ intercomparison during deployment/recovery from a small boat
...


(deployment_ship_CTD)=
## Calibration during deployment/recovery from a ship with a CTD rosette equipped with a calibrated oxygen sensor
...


## Piloting
...
In this section, specific piloting requirements during the mission execution which are needed to allow quality control are mentioned.
Towards the end of the mission power constraints often require the reduction in sampling frequency or even turning the sensor off. In case occasional sampling is performed, night sampling rather then daytime profile should be preferred. In most cases, daytime profile will be affected by non photochemical quenching and the absence of nighttime profile could limit data correction options.
At least one good quality up and down cast to the maximum deployment depth performed immediately prior to the pre-recovery samples being taken is recommended.
Coordination between the recovery group and the pilots is essential.

### Gather data to help correct for sensor response time
We sometimes do see hysteresis so maybe we want some text here too?

### Gather data to correct for sensor drift
#### Deep water masses
If the mission is carried out deep enough waters where the no fluorescence signal in deeper waters is a valid assumption, in-situ calibration points can be recorded. This data can not only be used to re assess dark count in case manufacturer calibration values are no longer valid but it can also give valuable info over possible sensor drift.

### Gather data for in-situ inter-comparisons
Other monitoring platforms, such as moorings can be used as an inter-comparison reference if the quality of these data is as good or better than from the glider.
The mission plan should aim to pass close to these platforms, ideally multiple times across the length of the mission.

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