[cf-satellite] Telemetry measurements as coordinate variables?

Hi.
While reading the CF conventions regarding coordinate variables, I found that coordinate variables are not supposed to have any "fill" values. This makes sense to me. Does this same restriction hold for a variable that is identified as an auxiliary coordinate via the "coordinates" attribute on another variable? If both variables are telemetry measurements, and thus subject to having missing values, can one be validly used as an auxiliary coordinate variable, or should this linkage not be made? The example pseudo-CDL below describes what I am wondering about. 

   dimensions:
        cycle = UNLIMITED;

   variables:
        double acq_time(cycle); // telemetry measurement
            string start_time:units = "seconds since ...";
            start_time:_FillValue = -999.3;

        float baseplate_temperature(cycle); //also a telemetry measurement
            string baseplate_temperature:units = "degrees C";
            baseplate_temperature:_FillValue = -999.3;
            string baseplate_temperature:coordinates = "acq_time";

Grace and peace,

Jim Biard

--
Jim Biard

Government Contractor, STG Inc.
Remote Sensing and Applications Division (RSAD)
National Climatic Data Center
151 Patton Ave.
Asheville, NC 28801-5001

jim.biard@xxxxxxxx
828-271-4330