Fly me to the moon
Ken Tapping, May 16, 2018
This is the first time I have had the opportunity to squeeze one of my favourite jazz titles into an astronomy article. Considering the rigours of the journey and the hostile environment on the Moon, why would an astronomer like to go there?
Doing astronomy from the surface of the Earth is difficult. All the cosmic emissions have to get through the atmosphere on their way to our telescopes. Some emissions are totally blocked, some partially blocked and most suffer some form of distortion. In addition, there is the problem of people…us. Our way of life involves squirting enormous amounts of light in all directions. This makes the sky glow and hides faint astronomical objects. Fortunately, we are now realizing that in addition to light pollution costing us huge amounts of money in wasted energy, it is degrading our enjoyment of the natural world. However, our telescopes are driving to higher sensitivities, making them more vulnerable to light pollution. Luckily there are still some truly dark locations.
Our radio telescopes are no better off. Manmade radio transmissions are everywhere. Our cars and even we ourselves carry at least one, maybe more active radio devices. WIFI is a fact of life and the demand for more radio services continues to grow. In addition to living with ground-based interference, radio telescopes have to look past aircraft with their own internet connections and satellites providing a multiplicity of services. Up to 10,000 satellites will be launched in the next few years in order to provide
At the moment there are no people and very few radio transmitters on the Moon, and no light pollution or sky glow. However, the Earth is still a problem. In the lunar sky it appears about four times the diameter of the Full Moon and shines three times brighter. The Earth is also enormously bright at radio wavelengths, because of our radio transmissions. There is a solution; we can put our telescopes on the other side of the Moon. Because the Moon rotates once for every orbit, we never see the other side, and it never gets to see us, so we won’t have to deal with its optical and radio glare. However, there is still the Sun. The far side of the Moon is often, and wrongly, referred to as the “dark side”. The Sun shines there too. When the Moon is New, it is day on the far side. When it is Full, it is day on our side.
There are downsides. The Moon has no atmosphere, so we will have to live in an airtight, radiation-screened base, probably underground, only going onto the surface as needed. There are huge temperature variations between lunar day and night, making it challenging to protect our mirrors and precision antennas from thermal distortion. Once we have beaten the challenges, our reward will be a better view of the universe than we have ever had before. So, why are we continuing to build our major new astronomical facilities on the surface of the Earth?
Until we have a manned base on the Moon, equipped with all the lab and workshop support we have here, lunar instruments will have to be treated as space projects. Because it is hard to get a service engineer to a broken space or lunar telescope in a timely fashion, we will need to spend months or years striving for an extremely high level of reliability. With ground-based telescopes, supported by workshops, lots of expert help and easy transportation, reliability is less of an issue, so instrumentation can be developed and deployed quickly. In addition, here on Earth, we can involve students in hands-on work on new instrumentation. One day, maybe in a couple of decades, we will be able to fly students to the Moon for their work, but not yet.
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