Maritime telescopes: Stabilisation requirements for optical vs. radio telescopes?

Question

SOFIA stands for Stratospheric Observatory for Infrared Astronomy. She says:

My telescope stays stable with a spherical bearing, shock absorbers, and gyroscopes.

I suppose a similar system would work for an optical telescope on a maritime vessel as well. But what about a radio-telescope on a ship with a dish of around 10m? What are arguments (ideally mathematical ones) against a similar construction like for SOFIA?

References

Tom Nardi A Miniature Radio Telescope In Every Backyard. hackaday.com (2019)
Gregory Redfern: Cruise Ship Astronomy and Astrophotography - The go-to astronomy resource for cruise travelers

I don't know of any shipborne radio telescopes for astronomical applications, but historically they have been quite common for spacecraft tracking, especially during launch and orbital insertion phases. Since the target's is moving fast an in a peculiar way, and since there is a single source at a single frequency, the tracking antennas "lock on" to the source and track its motion. This automatically corrects for any motion of the ocean-going vessel as it's indistinguishable from motion in the sky. Since this is not related to astronomy it would not be a suitable answer here. — uhoh, Feb 09 '21 at 00:34
for bits and pieces of how tracking a moving radio source is done see How exactly were the signals from quad dishes of Apollo Deep Space High-Gain Antenna or Russian B-529 processed for local control of tracking? and From whence (what ground stations) do the world's major space agencies receive signals from their missions? and Was the nutation problem of the Ulysses spacecraft successfully mitigated? If so, how? — uhoh, Feb 09 '21 at 00:40
and Why is the reflector on this millimeter-wave antenna spinning? and What were those motorized human-piloted platforms with helical antennas called (tracking launches)? keywords are "conical scanning" or "conscan". — uhoh, Feb 09 '21 at 00:40
https://en.wikipedia.org/wiki/File:Yuanwang_1_in_Shanghai,_2019-10-17.jpg and see also — uhoh, Feb 09 '21 at 01:03
@uhoh On 2nd thought, I was thinking of radio dishes with diameter of $10..20 {\rm m}$, to be specific, I had images of the Mullard Radio Astronomy Observatory in mind. — B--rian, Feb 09 '21 at 08:45
@B--rian but on ships, and doing astronomical research specifically? If this was never done, it's hard to answer what the stabilization requirements would be, it would be application specific and with no existing application... — uhoh, Feb 09 '21 at 20:13
@uhoh I am somehow intrigued by the idea to have a (large) ship-based radio or radar telescope, because one could move it around the globe, see e.g. https://astronomy.stackexchange.com/questions/40260/building-a-floating-ocean-going-giant-radio-telescope and I am still collecting pro and contra arguments. I find the fact that it has not done before attractive. — B--rian, Feb 09 '21 at 22:08
@B--rian The Earth rotates already, so all ground-based instruments are in a sense "moving". I guess ships allow you to configure an array the way you like, similar to how the VLA and ALMA move their dishes around to optimize the configuration for a given measurement. I guess you must be talking about an array because if its a single dish experiment then there's no benefit I can see to putting one on a ship compared to putting it on land. — uhoh, Feb 09 '21 at 22:41
@B--rian Arrays require stable or at least continuously measured 3D positions to wavelength-scale accuracy for each element; so direction stabilization is not the big problem, it's accurate continuous position measurement, or at least calibration. They can retrieve the 3D position information from arrays by simultaneous measurement of point-like calibration sources, but this assumes extremely steady rotational and orbital motion of the Earth, not a bunch of ships moving in ocean currents. One 10-20 meter dish on one ship seems almost pointless. — uhoh, Feb 09 '21 at 22:44

score 3 · Accepted Answer · answered Mar 15 '21 at 00:26

You asked for arguments against this, but I don't think there are any other than money. Consider the AN/SPQ-11 passive radar that was aboard the US Navy ship Observation Island. The actual receiver area is not as large (7M according to https://fas.org/irp/program/collect/cobra_judy.htm), but we could imagine a larger antenna being placed on a larger ship such as the USS Enterprise. The beam (maximum width) of the Enterprise is 41 meters, which could certainly accommodate a 10-20m dish.

I think the only reason this would not be built would be lack of funds. From an engineering perspective, it seems doable.

Maritime telescopes: Stabilisation requirements for optical vs. radio telescopes?

References

1 Answers1