The 200th anniversary of the establishment of the Royal Observatory at the Cape of Good Hope will be celebrated in 2020. Located in the leafy Southern suburbs of Cape Town, The South African Astronomical Observatory is the national centre for optical and infrared astronomy in South Africa.
In South Africa, through the Square Kilometre Array (SKA) and other projects, there has been a renewed interest in astronomy, its scientific marvels and implications.
The SKA is not a single telescope, but a collection of telescopes or instruments, called an array, to be spread over long distances. The SKA is to be constructed in two phases: Phase one in South Africa and Australia; Phase two expanding into other African countries, with the component in Australia also being expanded.
The 200th anniversary of the establishment of the Royal Observatory at the Cape of Good Hope will be celebrated in 2020
In SKA Phase 1, the 64-dish MeerKAT precursor array, which is currently under construction and expected to come online in the near future, will be integrated into SKA1 MID, with the construction of another 130 dishes. In total, SKA1 MID will count almost 200 dishes spread around the Karoo. SKA1 MID will conduct observations in many exciting areas of science, such as gravitational waves, pulsars, and will search for signatures of life in the galaxy.
The Square Kilometre Array South Africa (SKA SA)’s success is underpinned by open and inclusive institutions, fostering and leveraging interrelationships, promoting innovation that may be commercialised, and attracting, retaining and training suitable individuals.
The South African Astronomical Observatory
The observatory has been a part of the history of South Africa for close to 200 years and has contributed to the curiosity of how the universe works and how astronomers learn about the universe with exciting technology, research and discoveries. Originally this historic observatory – now known as the South African Astronomical Observatory – was established to keep shipwrecks from littering the Cape of Good Hope. The 200th anniversary of the establishment of the Royal Observatory at the Cape of Good Hope will be celebrated in 2020.
Under test at the South African Astronomical Observatory is a vacuum pump, pumping the WinCam cryostat down to 10 to the minus five millibar. The WiNCam (Wide-field Nasmyth Camera) instrument is an imaging camera system to be mounted on the new 1-m Lesedi telescope in Sutherland. It allows a wide field of imaging, 43-arcmin diameter, with a standard suite of astronomical filters
Established in 1820, at the convergence of the Black (Salt) and Liesbeek Rivers, the Royal Observatory Cape of Good Hope, today known as the South African Astronomical Observatory (SAAO), became the first scientific institute in sub-Saharan Africa. The Observatory, the grounds surrounding it and the associated buildings that have sprung up over the past 180 or so years, are paid scant attention by urban passers-by as they speed through the suburb of Observatory in Cape Town. Yet, delving into the history of its establishment reveals a wealth of historical and botanical findings.
Until the work of the SAAO began in 1820, the treacherous seas around the Cape of Good Hope saw more than 500 years of ships battering and crashing through the South Atlantic, with little to no usable stellar navigation established. Without the positions of the Southern stars accurately mapped, ships were often on their own, in unfamiliar waters and under unfamiliar skies.
In 1820, a young Fearon Fallows was sent by the Royal Society of Astronomers in the UK to the Cape of Good Hope to get a handle on those southern skies, and maybe help a few ships’ captains avoid disaster. According to published records Fallows was a brilliant astronomer and mathematician from the same small town of Cockermouth in the north of England that produced the brilliant poet William Wordsworth and less brilliant (but maybe more colourful) Fletcher Christian of Mutiny on the Bounty fame.
A fixture to assemble the WinCam cryostat, manufactured at the South African Astronomical Observatory in Cape Town
Despite his small-town beginnings, Fallows was talented enough to be dispatched to the other side of the world to accomplish a nearly impossible task – to get an observatory up and running while plagued by sand and dust storms, snakes, a lack of qualified stone masons (major stone work was required to stabilise early astronomical equipment), and the dreaded tablecloth clouds that could almost instantly block out the skies. But Fallows persevered, and the original structure for the observatory was completed in 1829.
Fallows was instructed to choose a suitable, dust-free site within close proximity of, and in direct line of sight of, Table Bay so as to pass on accurate visual time signals to ships anchored in the bay. The location also needed to be sufficiently east of Table Mountain so as to have a clear view of the sky. After investigating the (dust-free) Tygerberg hill, it was deemed unsuitable as it was prone to mists. The current site was chosen as it fulfilled most of the requirements, and also due to accessibility of water from the nearby Liesbeek and Black (Salt) rivers. It was described as ‘stony’ with ‘wild brushwood’ by the then carpenter of the building operations, AlexanderTait. Fallows reported that: “Whilst we were digging for the foundations among the hard, pot clay an innumerable number of snakes were thrown up by the workmen,” giving meaning to the original name of Slangkop (Snake Hill) for the site. The low brushwood referred to might well have been Renosterbos, Elytropappus rhinocerotis or some other renosterveld shrub.
Construction of the Observatory only commenced in 1825 and it became operational in October 1828.
Sadly, the struggle may have taken the ultimate toll on Fallows, who passed away only three years later – dead from recurring scarlet fever, and buried on the grounds of his now functioning observatory.
A Haas VF 8 vertical machining center has been supplied with a 2-axis trunnion rotary table to give 5-axis capabilities
Fallows’ plotting of the southern skies finally appeared in star catalogues in 1851, and his successor’s catalogue of Southern stars has been held as the basis of refined sidereal astronomy (a field that relates to constellations and their daily movements) in the southern hemisphere. The observatory’s measurements were so precise for their time – this is still only 1833 – that they accurately measured the distance of Alpha Centauri (our next closest star, almost four and a half light years away) to within 1/5 000th of a degree. As the SAAO notes, that’s like measuring the diameter of a penny from four kilometres away.
Southern African Large Telescope
The observatory eventually set up a campus of major telescopes in the small Karoo town of Sutherland, about four hours away from the main location in Observatory and a town known for experiencing the coldest nights in South Africa while during the day temperatures soar into the 30 degrees Celsius, in order to take advantage of its dark skies, with very little light pollution and mostly unfettered by clouds.
The Southern African Large Telescope (SALT) is the largest telescope in the Southern Hemisphere, with a mirror measuring 11.1 by 9.8 metres. It is located at the South African Astronomical Observatory near Sutherland, at an elevation of 1 798 metres.
Martin Visser, Craig Sass and Malcolm Hendricks, all from the South African Astronomical Observatory machine shop
SALT is located 15 kilometres outside of Sutherland. It is commonly misconstrued that the SKA project is also located in the vicinity of Sutherland. However, the Losberg site, which is the main SKA site, is located near Carnarvon in the Northern Cape. The distance between Losberg and Sutherland is approximately 260 kilometres by road.
SALT is based on the Hobby-Eberly Telescope (HET). SALT is fixed at an elevation angle of 53° and thus moves only in azimuth. It follows objects with a moving instrument package at the focal point of the telescope mirror. The mirror is made up of 91 identical hexagonal segments. SALT is designed specifically for spectroscopy of astronomical objects. Construction of SALT began in 2000, and it made its first observations in 2005. The primary partner in funding SALT is the National Research Foundation of South Africa. More than 20 research institutes and universities in Germany, India, New Zealand, Poland, the United Kingdom and the United States are also partners in SALT.
Manufacture and fabrication of instrumentation
The SALT project became a reality under the leadership of the late Dr. Bob Stobie, a previous director of the SAAO. He was tasked to acquire a new, bigger telescope to upgrade the 50-year-old facilities of the SAAO. SALT kicked off in January 2000, when a team of engineers started working on the project at the premises of the SAAO in Cape Town and was inaugurated in Sutherland in November 2005.
There is plenty of information to be found on the properties of the telescope and its imaging camera Salticam and the resulting astronomy and scientific discoveries. However, a little known fact is that the SAAO has its own machining facility located at the SAAO site in Cape Town.
The South African Astronomical Observatory has recently installed a new Kitamura Mytrunnion 4G supplied by WD Hearn Machine Tools
“The requirements on the design and fabrication of SALT instruments to deliver the capability and performance expected by the SALT consortium are demanding, particularly for astronomical and scientific imaging applications. The subject of astronomy has a fascination for most and with scientific discovery constantly under scrutiny from the world the design, fabrication, assembly, and testing of instruments used is severe,” said Craig Sass, Mechanical Workshop Manager at SAAO.
“Given the mass and volume constraints at prime focus of the SALT project most fabrication was initially outsourced. The basic concept and design for this telescope was based on the Hobby–Eberly Telescope (HET) at McDonald Observatory in Texas, US. The SALT was the second such telescope and started off its development process using the design of the HET. However, many aspects of this design were improved on,” explained Sass.
“Any instrument had to be designed to be capable of addressing the major science goals of the SALT consortium and enable SALT to be competitive with other similar aperture telescopes in the southern hemisphere.”
SAAO machine shop’s involvement
“Our machine shop has been established for some time operating with a few conventional machines to carry out machining of maintenance and wear part components for SALT. The emphasis of the machine shop started to change in 2003 when we purchased a 4-axis Maximart CNC mill and a Haas TL2 toolroom lathe.”
The GF Agie Charmilles SA 30 spark eroder, supplied by Retecon Machine Tools, was installed in 2011
“We needed to upgrade our equipment but management also took a decision that it needed to get more involved with the mechanical aspects of the telescope including design, machining and fabrication of instruments that would in future be integrated into the telescope. It would include associated fixtures, documentation, and other required processes and detailed items such as all of the fabrication requirements in detail including machining processes and schedules, coating and plating processes and schedules, and all other shop drawings and working drawings, schedules and processes reasonably required to fabricate all of the components and equipment comprising a new instrument conceptualised and designed by SAAO engineers and scientists.”
“Additionally all materials incorporated into the instrument shall be new and of high grade commercial quality, be sound and free from defects, both internal and external, such as cracks, laminations, blowholes, inclusions, or porosity, be able to withstand the environmental conditions listed and conform to at least the minimum requirements specified in the appropriate American Society for Testing and Materials (ASTM) Standards, or its equivalent.”
“The associated design, interface and software requirements would also be incorporated.”
SALT tracker upgrade utilising aerospace processes and procedures
The SALT Tracker was originally designed to carry a payload of approximately 1 000kg. At the time the current loading exceeded 1 300kg and more instrumentation, for example, the Near-Infrared (NIR) arm of the Robert Stobie Spectrograph (RSS), was being designed for the telescope. In general, provision also had to be made to expand the envelope of the tracker payload carrying capacity for future growth as some of the systems on SALT were running with small safety margins. It was therefore decided to upgrade the SALT Tracker to be able to carry a payload of 1 875kg. Before the project “Kick-Off” it became evident that neither SALT nor SAAO had the required standard of formal processes and procedures to execute a project of this nature. The Project Management, Mechanical Design and Review processes and procedures were adopted from the Aerospace Industry and tailored for our application. After training the project team in the application of these processes/procedures and gaining their commitment, the Tracker Upgrade Project was “Kicked-Off” in early May 2013. The application of these aerospace-derived processes and procedures, as used during the Tracker Upgrade Project, were very successful but there were still specific challenges that needed to be met while executing a project of this nature and technical complexity.
In the workshop is a Fanuc wire cut
“The Tracker Upgrade project is significantly larger in terms of budget and scope than previous projects executed by SALT Operations and therefore, before the project “Kick-Off”, it was decided to formalise, improve and tailor the processes and procedures used during the project, especially here at SAAO.”
“The project took us three years to complete with most of the components custom manufactured in our mechanical workshops, but not the structural work which was outsourced. We had already increased our process capabilities by adding more CNC equipment in 2010, so we had the machining capabilities. The machines purchased included a Haas VF 8 vertical machining center that came with a 2-axis trunnion rotary table to give us 5-axis capabilities, a Haas ST30 CNC lathe and a Fanuc wire cut.”
“We have subsequently purchased GF Agie Charmilles SA 30 spark eroder in 2011 and a CMM machine in October 2016.”
New Kitamura Mytrunnion 4G
“The new Mytrunnion 4G from Kitamura, supplied by WD Hearn Machine Tools, has a maximum work-piece diameter of 500mm on its rotary trunnion table and 400mm work height in the Z-axis, with the ability to accept billets up to 200kg. This ultra-high precision, simultaneous 5-axis machine has a tilting table that rotates -120 to +30 degrees in the A-axis, with a C-axis rotation of 360 degrees, both having a minimum indexing command of 0.001 degree.”
Components manufactured on the various machines
“The design of the Kitamura trunnion table delivers incomparable stiffness and rigidity that provides the ability to position the work-piece very close to the spindle for optimum machining performance. To carry most of the machining load it employs a trunnion type cylinder in the A-axis supported by double column bridge, with both sides of the cylinder system mounted squarely against the centre of the C-axis, thus offering a higher level of rigidity and accuracy. The Mytrunnion 4G uses a high precision roller gear cam mechanism in the 4th & 5th axes that further enhances the in-built zero-backlash capability of the machine.”
“This rigid machine design enables the powerful 15kW directly driven spindle, with a BBT40 taper, to maximise material removal rates. With the world’s fastest accelerating spindle, the Mytrunnion 4G gets to a maximum speed of 15 000rpm in just 2.3 seconds and comes standard with a 60 tool carousel and a Renishaw OMI-2T laser toolsetter.”
Application specific
“We are not a commercial outfit but rather an application specific mechanical workshop. This does result in downtime and to keep our machines busy we are now carrying out work for other NRF facilities. One such facility is iThemba LABS, a National Research Facility within the NRF and the premier atomic particle accelerator laboratory on the African continent and the only facility of its kind in the southern hemisphere.”
A Haas ST30 CNC lathe completes the CNC lathe lineup
“Besides enhancing proton therapy in the treatment of cancer iThemba LABS is involved in particle and nuclear research. We are machining inner column sleeves for radiation vile holders for them, producing 10 a month. The lead billet weighs 33 kilograms and we machine about three kilograms off it.”
“Now that we have more high tech machining equipment we will be offering our services to other NRF facilities.”
Tradition of firing the Noon Gun set by SAAO
Believe or not, but yes it really is. Originally the guns were fired according to a flare set off at approximately 12pm from the South African Astronomical Observatory. After seeing the flare the Noon Gun artilleryman would then fire the Noon Day gun. However, this became unreliable and the SA Navy began to use the City Hall clock situated at the Cape Town parade as the suitable time. However, this too became unreliable as they soon realised that, while the Noon Gun was using the City Hall Clock for the accurate time, the City Hall Clock was using the Noon Gun to reset their clock.
Nowadays, it is far more precise. An electrical signal is sent from the SAAO (which has an unfailingly accurate atomic clock) a few milliseconds before noon. This burst of energy zips across the telephone lines, ignites the firing cap on the cannon, sparks the gunpowder and Boom! the cannon is fired at 12pm sharp (not a millisecond off). Allowing for all locals to use the opportunity to check and reset their watches and for all unbeknown first-time visitors to jump out of their socks as they are given a rather startling introduction to Cape Town.
For further details contact the South African Astronomical Observatory on TEL: 021 447 0025 or visit www.saao.ac.za or www.salt.ac.za
