Applications for line-of-sight communications links between spacecraft
include data relay from LEO spacecraft, telecommunications between sa
tellites in GSO or LEO orbits, secure communications in military satel
lite constellations, and links to manned spacecraft. Optical technolog
y will be the preferred choice for many such applications due to poten
tial advantages of small antenna (telescope) size and low mass and pow
er. MMS has been leading the development of the technologies needed fo
r such terminals under the ESA funded SILEX(1) programme and two fligh
t models are now under integration. In parallel, a second generation t
erminal known as the Small Optical User Terminal (SOUT) has been devel
oped to elegant breadboard level under ESA funding. The advantages of
low mass and power can now be realised due to recent advances in semi-
conductor laser technology. MMS has combined its experience in SILEX a
nd SOUT to produce a concept for a small terminal which will be attrac
tive to users in the near-term. This retains essential features of the
SOUT such as the softmount interface, combined acquisition and tracki
ng sensor, and fibre coupled lasers. It also minimizes cost by re-usin
g SILEX derived electronics and other space qualified elements. The te
rminal has a 7 cm diameter telescope, a mass below 50 kg, and will pro
vide a 50 Mbps data link with SILEX. The main features of the terminal
are presented in this paper together with the chief applications whic
h are envisaged.