The development of a sub-millimeter（ 0. 1 mm to 1. 0 mm or 300 GHz to 3 THz） limb sounding technique has enhanced our knowledge of O3 processes. Sub-millimeter wave limb sounding is important because the sub-millimeter includes many spectral lines of trace gases

particularly the halogen family. This study aims to investigate the possibility of limb sounding of a high-flying vehicle plume. ARTS forward model is used to simulate the limb sounding of the plume compositions to study their sensitivity. The sub-millimeter wave limb sounding is sensitive to the concentration variations in H2 O

O2

OH

and HCl. When their concentration is increased five times

their limb sounding bright temperature will increase by 80 K

80 K

5 K

and 50 K

respectively. However

sub-millimeter wave limb sounding is not sensitive to concentration variations in CO

CO2

and NO. Based on a simulated trail of a vehicle flying at an altitude of 15 km

the sub-millimeter wave limb sounding radiance temperatures of the plume under different atmospheric backgrounds are calculated and compared; the different radiance temperatures of limb sounding and nadir viewing are also compared. The plume of the flying vehicle can be detected with a sub-millimeter wave limb sensor under any atmospheric background. However

it cannot be detected with the nadir viewing sensor. Therefore

the sub-millimeter wave limb sounding technique has an advantage over nadir viewing in detecting the plume of a high-flying vehicle

and its atmospheric background affects the limb sounding of the plume.