Court remands TMT sublease

[Guest]

The most ironic thing about this whole state of affairs is the person bringing the lawsuit that obstructed TMT is not even Hawaiian. He is some white college professor of 'Hawaiian studies' who can speak the language. Since many native Hawaiian lineage holders support TMT, a non-Hawaiian has placed himself in the high and mighty position of dictating to them what 'being Hawaiian' is. Where have we seen this before?

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You can't fix Samsara.

[ericlp]

I'm sure that china isn't the only one thinking of putting telescopes in the sky. Maybe one day, we can send robots to the moon, that will build a huge telescope there. Maybe TMT is just an illusion. Tho, let's not forget that here in hawaii, we need all the jobs we can get and money that can be pumped into UH for research. It certainly might be a waste of time to build TMT with technology advancing at such a pace. But, being how "Telescope Time" is so limited now and in demand, if TMT is not built I don't see the number of telescopes that we have now being decommissioned. If anything leases will be renewed.

Tho, I do think Ted is right, however, maybe in the next 10-15 years we'll see some real improvement with AI and Robotics to make it happen.

[TomK]

It's not so much whether AI or robotics are developed in the next decade or so, it's the cost of putting something into space that's the big obstacle. Ground based telescopes will provide the majority of science discoveries for many decades to come, space telescopes will make unique discoveries that can't be done from the ground, but cannot yet replace the capabilities of ground-based observatories. Building a telescope on the moon that will rival the TMT, GMT or ELT in our lifetimes? No, it won't happen.

Remember that ground-based telescopes are an awful lot cheaper than an equivalent observatory in space, and even more importantly, the instrumentation is easy to upgrade to use new technologies. That is not the case with space-based observatories. This means observatories on Earth can be upgraded and continue to operate for decades and remain competitive. The JWST will make wonderful discoveries, but after a decade or so will be another piece of space debris.

Ted keeps going on about optical array telescopes in orbit but fails to mention they immediately lose half the capability of ground-based telescopes, the ability to do spectroscopy. He also ignores the fact that if such a telescope was launched, it would still need to have an array of detectors as wide as the TMT's primary in order to provide the same resolution. That technology is decades away.

[SBH]

Seriously Ted? You look rediculous attempting to school a highly educated scientist and astronomer who is the Director of Operations of UKIRT, one of the most productive telescopes in the world. Have some respect.

[Tink]

One question I have on all this debate over land based versus orbiting telescopes is how is the clarity of the lens "picture" on orbiting as far as the stability of lens as the satellite "autocorrects" it's orbital path? I don't know if they have a computer to keep up with the random pitch and yaw while another computer is navigating the satellite, but technology always has a way of amazing me.

Community begins with Aloha

[MarkP]

So all the astronomy professionals pushing for the TMT, spending more than a billion dollars on it just don't know what they are talking about but us armchair astronomers on Punaweb do? Whoodathunkit? Me, I would have been embarrassed to voice such an opinion. Shows how little I know.

[TomK]

This is just the usual pahoated abusive rant when his errors are pointed out. It's sometimes amusing, but I suspect in most cases he simply doesn't understand the subject well enough to know when he's posting utter bollocks. As for DSPs (digital signal processors), I've been working with them for the last couple of decades at UKIRT, so I really don't know why he decided to bring that up.

Tink - both ground-based and space based optical/infrared telescopes use guide stars to remain pointing precisely at whatever object they're observing. For ground-based telescopes the guide signal is fed to a computer controlling the mount (i.e., the main part of the telescope that controls telescope slews and positioning) and a computer that controls the secondary mirror (the mirror at the top of the telescope). Although the mount drives tend to be very accurate in tracking a target, small errors build up and changes in the guide signal will be sent to the mount computer to correct the pointing. These errors build up slowly so it's easy for the whole telescope to make small corrections. The signal sent to the secondary is generally used to correct for aberrations caused by the atmosphere. The secondary mirror is much smaller than the primary and can therefore be moved much faster. Our system typically operates at 50-100 Hz, i.e., 50-100 corrections are made every second - it improves our delivered image quality by a factor of two compared to uncorrected observations.

For orbiting telescopes, the same principle applies, but they don't have to correct for atmospheric conditions, so the guide signals are used to make small corrections in the satellite's pointing. You might be interested in how the Hubble does this:

http://goo.gl/rlI17M

The Hubble uses "reaction wheels" to make these corrections. Essentially, it uses basic physics to keep pointing accurately and to slew to new targets. If the telescope needs to move, the computer/gyroscope system instructs the wheels to spin. As a wheel spins in one direction, Newton's 3rd law takes over and the telescope moves in the opposite direction. Hubble has four such wheels aligned in different directions so it can move in any direction.

Hope that helps.

[TomK]

Tink - looked at your question again and realized I missed something out.

For space-based observatories such as the Hubble, they are in orbit so can generally be left alone when it comes to navigation. Once you get something into space it generally follows what it thinks is a "straight line". In orbit, that "straight line" is basically being in free-fall towards the center of the earth but is countered by its speed around the planet. It falls to earth but at the same time its speed balances that and it remains in a stable orbit (it's like spinning a ball on a piece of string - look up "centripetal acceleration" if you get the chance).

Because most space-based telescopes are in low earth orbit, they do still encounter a few molecules of our atmosphere which causes drag, slows them down which means their orbit becomes lower. There are some gravitational effects that are incredibly hard to calculate that change the orbit over time as well. (Did you know that the movement of Kilauea's lava or magma affects the orbits of satellites in low earth orbit? It does). Every so often that has to be corrected so the observatory, or any controlled satellite, will be commanded to fire its thrusters to put it back into a slightly higher orbit.

The Hubble doesn't do that because the gases would remain near the telescope and potentially affect observations. Instead, it uses a particularly ingenious technique. It turns on electromagnets which interact with the earth's magnetic field. They repulse each other which moves the Hubble away from the planet. It's a slow process, but it doesn't need to be quick.

Apologies for taking this away from Puna and Hawaii, but Tink reminded me of an undergraduate report I had to write many years ago, and this stuff has just stuck in my head. Just a very elegant use of physics.

I now return you to your normal programming.

[TomK]

Sorry, one more interruption.

PT scribbled:

"Also, optical astronomy has reached the point that radio telescopes are providing more information about the nature of the universe beyond optics."

I've read this over and over again and it still makes no sense. Therefore it's time for this again:

http://goo.gl/chfjSt

[Tink]

Mahalo Tom for your response to my question. Interesting that the magnetic field in lava (magma) affects space navigation when it is flowing. I guess in a way we could call flowing lava "gravity fluid".

Community begins with Aloha