Low work function amorphous carbon Transfer Mold field emitter arrays (a-C-FEAs) have been fabricated by combining the Transfer Mold emitter fabrication method and the emitter material coating method to realize stable vacuum nanoelectronic devices in harsh environments of aerospace. The emitter tips of a-C-FEAs are extremely sharpened to 26.7-30.7 nm of tip radii. Work function of a-C-FEAs was as low as 3.6 eV compared with those of conventional emitter materials such as carbon nanotube of 5.0 eV. Oxygen radical flux intensity of 1015 atoms/cm2•sec was used for the evaluation of field emission characteristics, whose value is 107-108 times higher than those of 107-108 atoms/cm2•sec in aerospace of satellite orbits. As the oxygen radical treatment time increased, turn-on fields of Ni-FEAs exhibited the 2.2 times degradation from 14.9 V/µm to 32.7 V/µm. Those of a-C-FEAs have been keeping almost the same value of 20.8-23.7 V/µm after oxygen radical treatment. The a-C-FEAs exhibit stable field emission characteristics in harsh environments.