  The Smithsonian Astrophysical Observatory (SAO), a member of the Center for
Astrophysics | Harvard and Smithsonian, is in discussions with the Space
Applications Centre (SAC) of the Indian Space Research Organization (ISRO) and
its partners in the newly formed Indian Sub-millimetre-wave Astronomy Alliance
(ISAA), to collaborate in the construction of a sub-millimeter-wave astronomy
observatory in the high altitude deserts of the Himalayas, initially at the
4500 m Indian Astronomical Observatory, Hanle. Two primary science goals are
targeted. One is the mapping of the distribution of neutral atomic carbon, and
the carbon monoxide (CO) molecule in higher energy states, in large parts of
the Milky Way, and in selected external galaxies. Such studies would advance
our understanding of molecular hydrogen present in the interstellar medium, but
partly missed by existing observations; and characterize Galaxy-wide molecular
cloud excitation conditions, through multi-level CO observations. Stars form in
interstellar clouds of molecular gas and dust, and these observations would
allow research into the formation and destruction processes of such molecular
clouds and the life cycle of galaxies. As the second goal, the observatory
would add a new location to the global Event Horizon Telescope (EHT) network,
which lacks a station in the Himalayan longitudes. This addition would enhance
the quality of the images synthesized by the EHT, support observations in
higher sub-millimeter wave bands, sharpening its resolving ability, improve its
dynamic imaging capability and add weather resilience to observing campaigns.
In the broader context, this collaboration can be a starting point for a wider,
mutually beneficial scientific exchange between the Indian and US astronomy
communities, including a potential future EHT space component.
