Measurement Timing + …

Start time, end time and time reference are important parameters for a measurement setup. The time reference can be set to UTC or local time which is UTC + time shift [h]. The radiometer determines UTC from a GPS clock reading which is updated every 10 minutes.
There are two ways of triggering a measurement: Immediately after launching the measurement batch or at a certain time and date. Using a start time before the current time is equivalent to an immediate start. If the measurement start is triggered to a certain time, the check boxes Ignore Date and Ignore Hour allow for a date or hour independent triggering. This is particularly useful in a repeated multiple MDF batch measurement, where MDFs are repeated multiple times. A triggering to a certain date / time would trigger the MDF only once but not repeatedly. E.g. if Ignore Hour is checked (‘Triggered’ mode activated) and the ‘Start Time’ entry is set to 22|36|15, the measurement is triggered to 00:15:00, 01:15:00, 02:15:00, …, ignoring the current date and hour. If a more frequent trigger is required, one can use the Raster feature combined with a raster period. E.g. if a start time of 22|36|15 is defined in combination with raster mode and a raster period of 10 minutes, the trigger sequence is: 22|36|15, 22|36|25, 22|36|35, 22|36|45 etc.
Two options are available for measurement termination. In LIMITED mode the user can set a duration or termination time. If the stop time is before the start time, the measurement duration is adjusted to 100 seconds.
In the case that the measurement has a well-defined end time (automatic measurement termination, LIMITED mode) the radiometer needs a filename for storing backups. The user may enter any filename not longer than 8 characters. The host also uses this filename when it is operated in automatic storage mode. If measurement timing is set to UNLIMITED mode the radiometer automatically generates filenames deduced from the actual time and date and ignores the measurement filename entry.
In UNLIMITED mode the user must terminate the measurement manually. A new filename is generated every X hours where X is selected from the ‘New Filename every’ list box. The file
format is one of 14 possible versions given in the ‘Filename convention’ list box. In the format string HH=hours, DD=days, MM=month and YY=year of the actual time and date. During measurement this filename is also transmitted to the host, which uses it for file storage of monitored data (assuming that the host is operated in “Automatic Storage” mode).
Since the temperature and humidity environmental sensors respond quickly to changes of the corresponding parameters (caused by turbulence in the vicinity of the radiometer) it is sometimes desirable to smooth the data samples of temperature and relative humidity. This is important if retrievals are utilizing the meteorological sensors, but the detailed surface turbulence at the radiometer location are not of interest and thus only lead to noisy retrieval results if not filtered. In Data Smoothing one can activate a 10 minutes LIFO filter to smooth the environmental temperature and humidity readings.
A humidity threshold can be defined for setting the dew blower fan speed to full power.
Another feature of the Timing+… tab sheet is the enabling of a file backup on the embedded PC. When backup is enabled, the checked products will be automatically stored in the radiometer’s data directory. This is usually done for safety reasons because the standard mode of measurements is to enable automatic data storage on the host (online monitored data). With this method the data transfer virtually does not require any time. Without monitoring the data on the host and only storing it on the radiometer as backup the user will sooner or later have to transfer the data from the embedded PC to the host using the Transfer Data and System Files menu.
For the RPG-HATPRO, RPG-TEMPRO, RPG-HUMPRO and RPG-LHATPRO, the radiometer PC performs quality checks on the water vapour and oxygen lines measured in zenith mode and during boundary layer scans. These tests include the detection of possible external interferences or reduced quality level 2 data caused by intensive rain. The program generates a quality flag and information for the possible reason of a reduced quality. This information is coded into the rain flag of each sample (see Appendix A). More information about quality checking can be found in appendix A18. The radiometer can be programmed to filter low and medium quality samples and is capable of interpolating the brightness temperature of channels affected by external interference. In Level 2 Data Quality there are three options for filtering level 2 data (retrieved atmospheric data). The Flag Data Quality (Level 2) option does not filter the level 2 data according to the quality level but flags each data sample in the rain flag byte as described in appendix A. The user has to filter the data samples himself but can use the quality information in the rain flag byte. With option Remove Medium / Low Q., medium and low quality samples are not transmitted by the radiometer. In this case, the sample sent to the host is the repeated latest high quality sample. The filter Remove Low Quality will only remove the worst quality level data and transmits high and medium quality data. If the radiometer detects a possible interference problem (an external signal interferes with one of the receiving channels), it can automatically remove the interference signal from the spectral line by interpolating between adjacent channels. This feature can be enabled by checking Remove Interferences.
Another feature is the possibility of blanking or avoiding the position of the sun during scanning observations and sky tipping. This implies that the azimuth positioner option and GPS clock are installed and that the azimuth table is precisely aligned according to the procedure described in section 8.2.2. If the Avoid Sun in Scans checkbox is marked, the radiometer will determine the sun position on the sky automatically when performing full sky scans, azimuth scans (Hovmöller plots) or sky tipping calibrations. If the sun position is encountered, the radiometer sidesteps this position by about 6° to avoid unrealistic brightness temperatures in transparent channels.