  AMIGO is a first-generation Astrodynamical Middle-frequency Interferometric
GW Observatory. The scientific goals of AMIGO are: to bridge the spectra gap
between first-generation high-frequency and low-frequency GW sensitivities; to
detect intermediate mass BH coalescence; to detect inspiral phase and predict
time of binary black hole coalescence together with neutron star coalescence
for ground interferometers; to detect compact binary inspirals for studying
stellar evolution and galactic population. The mission concept is to use time
delay interferometry for a nearly triangular formation of 3 drag-free
spacecraft with nominal arm length 10,000 km, emitting laser power 2-10 W and
telescope diameter 300-500 mm. The design GW sensitivity in the middle
frequency band is 3 x 10^(-21) Hz^(-1/2). Both heliocentric and geocentric
orbits are under study. All options have LISA-like formations, that is the
triangular formation is 60 deg inclined to the orbit plane. For AMIGO, the
first-generation time delay interferometry is good enough for the laser
frequency noise suppression. We also investigate for each options of orbits
under study, whether constant equal-arm implementation is feasible. For the
solar-orbit option, the acceleration to maintain the formation can be designed
to be less than 15 nm/s2 with the thruster requirement in the 15 {\mu}N range.
AMIGO would be a good place to implement the constant equal-arm option. Fuel
requirement, thruster noise requirement and test mass acceleration actuation
requirement are briefly considered. From the orbit study, the solar orbit
option is the first mission orbit choice. We study the deployment for this
orbit option. A last-stage launch from 300 km LEO (Low Earth Orbit) to an
appropriate 2-degree-behind-the-Earth AMIGO formation in 95 days requires only
a {\delta}v of 75 m/s.
