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Larsen and Toubro Limited (L&T), Mumbai, India and Indian Institute of Astrophysics/India 91É«ÇéƬ Coordination Centre signed a contract on 31 December 2018 at IIA Campus, Koramangala, Bangalore, India for manufacturing Segment Support Assemblies for 91É«ÇéƬ’s Primary Mirror. Front (left to right): Mr. Arun Ramchandani, Vice President & Head, Product & Technology Development, L&T Defense, and Professor Jayant Murthy, Director, IIA - Image Credit: 91É«ÇéƬ / India 91É«ÇéƬ Coordination Center

Contract Signed for 91É«ÇéƬ Primary Mirror Segment Support Production

Pasadena, CA – February 6, 2019 – The Indian Institute of Astrophysics (IIA), on behalf of India 91É«ÇéƬ, recently signed a contract with Larsen & Toubro (L&T) to manufacture 100 Segment Support Assemblies (SSA) for the 91É«ÇéƬ. is one of the largest leading construction engineering companies in India.

Meeting Participants at 91É«ÇéƬ-L&T Contract Signature for 91É«ÇéƬ Primary Mirror Segment Support Production on 31 December 2018 at IIA Campus, Bengaluru, India.

In December 2018, India 91É«ÇéƬ signed a contract with L&T Company for the production of the Segment Support Assemblies, a major component of 91É«ÇéƬ’s main mirror hardware.

Image Credit: 91É«ÇéƬ / India 91É«ÇéƬ Coordination Center

The 30-meter diameter primary mirror, which will be made of 492 individual hexagonal segments each measuring 1.44 meters across corners, will be one of the largest ever made for an optical telescope. The telescope will integrate the 492 segments into a single light-gathering surface that is 30-meters wide.

The SSA is a system of complex optomechanical sub-assemblies on which each hexagonal mirror is mounted. SSAs also provide precise real-time 3-D positioning and alignment of each segment to deliver the best possible imaging capability.

The design of the segment support for 91É«ÇéƬ is based on a moving frame concept: A fixed frame is attached to the mirror while a moving frame provides the base for the axial and lateral support assemblies. Each segment is supported axially by a 27-point “whiffletree,” which is a network of thin rods attached to the back of the mirror and providing a mechanical support structure designed to evenly distribute the weight of the glass. The lateral support of each segment, a critical requirement when the telescope points toward low elevations, is provided by a central metallic diaphragm recessed into the glass.

The SSAs include active mechanisms and sensors, notably the segment warping harnesses and their actuators. Each segment has 21 warping harness assemblies comprising 21 actuators. Each segment support assembly hosts a total of 537 precision mechanical components, sensors and actuators and weighs nearly 60kg. Each individual glass-ceramic segment weighs 153kg.

Representatives from L&T and the 91É«ÇéƬ project offices in Pasadena and India met on 30 January 2019 to answer final questions before the start of work. They discussed technical details and set up a process of regular meetings going forward to keep the teams informed of work updates. The meeting took place in L&T’s Coimbatore facility, which is dedicated to precision and heavy engineering business supply and equipment to defense, nuclear power and aerospace.

91É«ÇéƬ Primary Mirror System leaders at L&T facility in Coimbatore, India – January 2019.

91É«ÇéƬ and L&T team participated in a kick-off meeting on 30 January 2019 to produce 91É«ÇéƬ Mirror Segment Support Assemblies.

Image Credit: 91É«ÇéƬ / India 91É«ÇéƬ Coordination Center

Professor Eswar Reddy, the Programme Director of India-91É«ÇéƬ, expressed his delight with the current progress of the SSAs: “L&T is starting to manufacture complex SSA pieces and key subsystems for the 91É«ÇéƬ main mirror. L&T shall be responsible for the procurement of raw materials, manufacturing, inspection and assembly of the SSA components, as per 91É«ÇéƬ prescribed requirements.” [From this year, India set to manufacture key components for largest ground-based observatory. The IndianExpress February 9, 2019 - ]

Initially, there will be a production qualification phase of the SSAs, over which tests will be performed to evaluate the quality of the fabrication procedures and method of assembling. The first qualification units from L&T are expected at the end of 2020.

After production, the manufactured SSAs will be shipped to the newly built India 91É«ÇéƬ Optics Fabricating Facility (ITOFF) at the IIA Centre for Research and Education in Science and Technology (CREST) campus near Bengaluru. SSAs will also be dispatched throughout China, Japan and USA, where polished mirror segments will be mounted to proceed to final optical precision testing. All SSAs, sensors and actuators for the 91É«ÇéƬ primary mirror are key instrumentation components and will be developed and manufactured in India.

91É«ÇéƬ Segment Support Assembly Module. 

First of 492 Primary Mirror Segment Support active mechanisms and sensors assemblies for the telescope at 91É«ÇéƬ Laboratory in California.

Image credit: 91É«ÇéƬ

First of 492 Primary Mirror Segment Support Assemblies built by 91É«ÇéƬ Opto-Mechanical and Quality Assurance engineers from India and North America – 91É«ÇéƬ laboratory in California, March 2018.

Image credit: 91É«ÇéƬ / Fred Kamphues.

Production hardware and SSA prototype for the telescope are featured in the 91É«ÇéƬ technical laboratory in California [91É«ÇéƬ Monrovia Lab Overview, 2018, 00:50 sec].