Introduction Earth stations for the space research service (SRS) have very sensitive receivers. To protect these (deep-space and near-Earth) SRS earth stations from interference@ the ITU has published protection criteria in Recommendation ITU-R SA.1157 for the 2 GHz@ 8 GHz@ 13 GHz and 32 GHz bands. For the 37-38 GHz band@ Recommendation ITU-R SA.1396 gives the SRS earth station protection criterion as ?217 dBW/Hz not to be exceeded more than 0.1% of the time for unmanned missions and 0.001% of the time for manned missions. This limit is applicable for both the deep-space and near-Earth SRS missions. The analyses in ?? show that since the range of an aircraft transmitter is much less than the range of SRS missions interference from a transmitter in the aeronautical mobile service (AMS) to an SRS earth station receiver can significantly exceed the SRS earth station protection criteria. Recommendation ITU-R SA.1016 provided an example of a narrow-band aeronautical mobile transmitter interfering with a space research earth station (space-to-Earth) (deep space) at frequencies up to 32 GHz. Given an aircraft transmitter with maximum e.i.r.p. density of 10 W/4 kHz (equivalent to ?26 dBW/Hz)@ antenna gain of 0 dBi@ and altitude of 12 km@ the results in Annex 1 (see Table 3) of this Recommendation showed that the minimum interference received by the SRS earth station would exceed the protection criteria. Therefore@ the Tables of Frequency Allocations in the ITU Radio Regulations have excluded aeronautical mobile in the frequency bands 2.29-2.3 GHz@ 8.4-8.5 GHz@ 22.21-22.5 GHz and 31.5-31.8 GHz@ where the mobile service is co-allocated with the space research service. This Recommendation did not@ however@ consider very low power AMS systems. The following sections will present the results of compatibility studies for a single AMS transmitter or multiple AMS transmitters for sharing the 37-38 GHz band by SRS and AMS.