AtmSfcInterp in UFO

I tried to add something into the AtmSfcInterp. However, I noticed that that obs operator is not activated, and no corresponding ctest is available. I tried to test it with dummy data, but encountered

AtmSfcInterp does not exist in ufo::ObsOperatorFactory.
ABORT: Element does not exist in ufo::ObsOperatorFactory.

Is it turned off intentionally?

Thanks

Youhua