At the time, it was the most advanced radio telescope in the world, incorporating many new innovative design features that have since become standard in all large dish antennas.

Through its early discoveries it quickly became the leading instrument of its kind in the world.

Today, 60 years after it was commissioned, it is still arguably the finest single-dish radio telescope in the world.

It is still doing world-class science and making discoveries that are shaping our understanding of the Universe.

In the lead up to the anniversary this Sunday, CSIRO's operations scientist, John Sarkissian OAM, walks us through how The Dish came about, and all that the telescope has achieved over the past 60 years.

In Part 4, the final article, we look at all the telescope has achieved since it was officially commissioned.

The telescope was originally expected to have a lifetime of twenty years, which it has now well and truly exceeded.

There have been many reasons for this longevity.

Its location in the Goobang Valley, just north of the town of Parkes in the Central West of NSW, was chosen for its lack of radio frequency interference (RFI).

A large antenna like Parkes is incredibly sensitive to local radio interference, and the region around the Goobang Valley shielded the telescope from the radio emissions from the larger population centres further east such as Orange, Bathurst, Lithgow and of course, Sydney.

Today, the situation has worsened: it seems like everyone has mobile phones, digital cameras, GPS receivers, computers, microwave ovens, digital TV, wireless internet and much more.

All of these devices emit radio signals that can easily overwhelm the faint signals the astronomers want to detect from space, though despite this, useful work can still be undertaken at Parkes.

Another great advantage of the site is its location on the Earth's surface.

From these latitudes the centre of the Milky Way passes almost directly overhead, so the richest and most interesting parts of the Galaxy are easily accessible from Parkes and gives it an advantage over almost all other large radio telescopes.

Another reason for its success was its design.

The famous British engineer, Barnes Wallis, of 'Dam Busters' fame, suggested many new, innovative design features.

However, the innovative features alone do not explain the longevity of the telescope, rather, the telescope has been constantly upgraded over the years.

The most obvious upgrades have been to the dish surface.

Beginning in 1970, the surface has been progressively upgraded, with the most recent surface upgrade in 2003.

Another major upgrade was to the focus cabin in 1995, meaning it is capable of housing up to four radio receivers. This has made the telescope more frequency agile and efficient in the way it is used and has increased the productivity of the telescope many-fold.

Another source of the telescope's success has been the constant upgrading of its processing instrumentation.

When it was first commissioned, the most common recording device was a chart recorder and analysis was performed with a slide-rule.

Eventually, the Observatory's first computer was installed in 1968, but since then, every function of the telescope has been fully computerised.

We've moved from chart recorders to supercomputer clusters utilising the latest GPU and radio frequency over fiber-optic technologies. It's been an incredible transformation.

The telescope's receiving systems have also been extensively upgraded over the years.

When commissioned, simple dipole receivers were used to detect the radio waves at the focus.

These essentially operated at room temperature and were not very sensitive, but eventually cryogenically cooled receivers were developed that operate around 20K (minus 253 degrees celsius), vastly increasing their sensitivity.

In 1997, this technology was further advanced when the 20cm multi-beam (MB) receiver was commissioned.

This allowed astronomers to 'see' 13 points simultaneously on the sky and to conduct surveys 13 times faster than with conventional receivers.

You can think of it as a 13-pixel radio camera. It's not much compared to today's multi mega-pixel optical cameras, but it was a great improvement on the single pixel, conventional radio receivers.

This MB receiver rejuvenated the Parkes telescope.

It led to several ground-breaking surveys that doubled the total known number of pulsars, including the discovery of the only known double pulsar system in 2003.

It also allowed astronomers to probe the Universe and plot the positions of galaxies out to 300 million light years and to peer through the obscuring dust of the Milky Way to see what lay beyond for the first time.

The sum result of all these upgrades, both external and internal, is that today, the Parkes telescope is over 10,000 times more sensitive than when it was built.

In fact, the only parts of the telescope that are 60 years old, are the concrete and steel it is made of. In many ways it is a young telescope.

The way the telescope operates has also changed over time.

At first, dedicated telescope drivers were employed to drive the telescope for the astronomers.

The old control desk, with its dials and globe (which resembled something from The Thunderbirds) was too complicated to entrust to inexperienced astronomers, but over time, this became a very inefficient and costly way of operating the telescope.

With new equipment and observing techniques being developed, it was time for a change, so in the early 1980's, the entire control system was replaced by a new computerised system, and this even helped to free up money to develop new equipment and to build a new observatory - the Compact Array - at Narrabri.

In the late 2000's, it was decided to upgrade the operations again and allow remote observing to be undertaken - an eerie nod to COVID 'work from home' times!

The entire control system was modified so that astronomers could connect via the internet and safely control the telescope from a remote location, such as their office or home, from anywhere in the world.

The improvements to the telescope have meant that new discoveries are being made all the time, and one fine example is the discovery of Fast Radio Bursts (FRB's), which are sudden, single bursts of radio energy that last only a few milliseconds.

Their origin is a complete mystery, but from the nature of the signals detected so far, they appear to come from extragalactic sources, billions of light years from the Earth, which implies that the energy release is enormous.

The first FRB was discovered at Parkes in 2007 by British astronomer, Duncan Lorimer, and his colleagues.

He was searching through some archived data taken with the MB receiver in 2001, looking for giant pulses from pulsars, but instead he came across an ultra-bright burst from a single point on the sky.

With the MB receiver, Parkes was the ideal place to discover them.

Many theories have been advanced to explain them, such as colliding neutron stars or black-holes, and even signals from extra-terrestrial civilisations, but to date, their origin is still a mystery.

Another new form of receiver developed by CSIRO is a Phased Array Feed (PAF) receiver.

PAFs are many little antennas placed on the focal plane of the telescope, and each of the antennas can be linked together, or phased, in such a way that many points on the sky can be observed simultaneously.

These PAFs were developed by the CSIRO to operate on the next generation of radio telescopes and can observe as many as 36 points on the sky at once.

In 2020, work began on a cryogenically cooled PAF specifically for the Parkes telescope, and this cryo-PAF receiver will be even more sensitive than the existing PAFs and will be capable of observing twice as many adjacent points on the sky.

The receiver will be installed in 2022, with preparation work beginning in November 2021. It will be an ideal instrument for searching FRBs.

Since 2016, the Breakthrough Prize Foundation in the United States, began a Search for Extra-Terrestrial Intelligence (SETI) project. This global initiative is known as Breakthrough Listen and will run for ten years.

The Parkes telescope is essential for the scientific integrity of the Breakthrough Listen program, because it is ideally located and perfectly positioned to provide the best and most powerful view of our galaxy.

The chances of finding anything are very small, but the consequences are enormous. For this reason, it is an extremely worthwhile undertaking.

Though Parkes was designed primarily as an astronomical instrument, its innovative design was recognised early on by NASA to be a near-ideal instrument for tracking spacecraft in deep space; that is, at the orbit of the Moon and beyond.

In 1960, one year before the telescope's construction was complete, the CSIRO was approached with a proposal to include the telescope in NASA's fledgling, Deep Space Network (DSN).

The CSIRO agreed that whenever a strong, reliable signal was required, especially during critical moments like planetary flybys or landings, the Parkes telescope would support the missions for those brief periods.

Consequently, beginning in December 1962, Parkes tracked the very first interplanetary mission, Mariner 2, as it flew by Venus.

This was a test track that proved to be so successful that NASA decided to model its planned large tracking antennas on the Parkes telescope's design, which is why they were all originally 64-metres in diameter.

Other tracking missions

But the story hasn't finished yet.

Earlier this year, CSIRO signed a contract for Parkes to track the next generation of commercial lunar landers, beginning in early 2022.

These missions will continue the proud legacy of Parkes' involvement in space tracking.

The great advantage of the Parkes telescope has been its incredible flexibility and versatility.

Although it was initially designed as a survey instrument, its versatility has meant that it can perform many different types of observations: from discovering quasars, pulsars, and molecular clouds to tracking spacecraft or searching for ET.

It can do many things efficiently - and very well.

But in the end, what makes Parkes such a great instrument are the people who use it - the engineers and programmers who design and build the new equipment, and the people who maintain it.

This attracts the very finest astronomers, who devise new observing techniques and clever ways to extract more information from the data.

It is these people who realise that a new, unusual signal is interesting and worth following up on, with a curiosity to get to the bottom of a mystery.

READ MORE ABOUT THE DISH'S 60TH ANNIVERSARY:

- Where it all began

- From a dream to a reality

- Construction and commission

The Parkes telescope has been fortunate to have these inspiring people work on it.

Parkes has maintained its world-leading position in radio astronomy by constantly adapting and changing to meet new requirements.

Today's improvements and upgrades are just the latest in a spectrum of change that has made the CSIRO's Parkes telescope Australia's premier scientific instrument.

It is an iconic telescope with a great legacy of world-class science and discovery.

Sixty years after its commissioning, the future still looks bright at Parkes.

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