Fortaleza: The Next Generation of VLBI Telescopes

Haystack is designing and installing the signal chain for a new NASA radio telescope in Fortaleza, Brazil.

  • Whose telescope is this?
    The new radio telescope is being commissioned by NASA’s Space Geodesy Project (SGP). The SGP radio telescopes are also part of the International VLBI Service for Astrometry and Geodesy (IVS) network, which includes VLBI telescopes around the world.
  • What’s a radio antenna/telescope?
    Radio antennas, sometimes called radio telescopes, are large dishes that collect information in the radio portion of the electromagnetic spectrum. Everything in the universe emits energy, and radio science examines radio waves from objects in space, such as quasars, to learn about space. We also use radio waves in a technique called Very Long Baseline Interferometry (VLBI), that lets scientists precisely measure some interesting properties of the Earth and how they are changing.
  • Why is the new telescope going to be in Brazil?
    Most of the NASA radio telescopes used in VLBI work are located in the Northern Hemisphere. Fortaleza has an existing observatory at this location, which makes it easier for the new dish to be installed and operated. Plus, its location in the Southern Hemisphere will improve the quality of geodetic data products obtained by the NASA radio telescope network.
  • What is Haystack doing for the new Fortaleza telescope?
    MIT Haystack Observatory has built several signal chains for NASA’s radio telescopes, and will be building the signal chain for Fortaleza as well. We’re really excited about this project and can’t wait to see the telescope ready to go!
  • What is a signal chain?
    In essence, the signal chain is the heart of the radio telescope: its non-metal parts. That is, it’s all the electronics. The signal chain includes all of the components necessary to detect and convert the incoming radio waves into digital recordings that can be further processed and analyzed by scientists. You’ll learn more about this as the building of this signal chain is completed and described in this blog.
  • What makes this network the “next generation” of radio telescopes?
    VLBI is a very well established technique: it has been in use for decades. The IVS and its member organizations such as NASA have designed the VLBI Global Observing System (VGOS) with updated and improved modern technology, such as smaller, faster-slewing antennas and a broadband signal chain to get the best data via VLBI. Fortaleza will be the latest NASA VGOS radio antenna, alongside others in Texas, Hawaii, Maryland, and right here in Westford, Massachusetts.


A close-up on an antenna's feed, with a round metal plate at the end
Feed interface plate (photo credit: Darryl Lakins)

OCTOBER 2, 2023

Good news, everyone! The FAT (that’s Factory Acceptance Test) went well, and the interface plate and its new VGOS antenna passed with no major issues. Congratulations to all teams working on this complicated project.

SEPTEMBER 27, 2023

Remember this thing? It’s the feed interface plate that will join the ISI-built antenna and the Haystack-built feed. The plate is now winging its way north [UPDATE: it has arrived! see image], courtesy of our shipping manager Don Sousa, enjoying a field trip to our colleagues in Canada for the factory acceptance test (FAT). More updates to follow, hopefully with good news, and maybe maple foliage photos!

AUGUST 31, 2023

An illustration of a computer board with many different colored lines and intersections against a black background
The upgraded VLBI Data Acquisition (VDAQ) board

A major milestone was recently achieved in the Fortaleza antenna build! On August 22, 2023, NASA held an important meeting. The official title is the “FGO Element Design Review (EDR),” but it is known here as a delta-CDR.

That’s a lot to unpack. NASA uses Systems Engineering terminology; CDR here stands for Critical Design Review. The “delta” part of the delta-CDR means that NASA is reviewing changes put in place in the current, updated space geodesy antenna signal chain design versus the design of the previous antenna (also done by the Haystack team).

Good news: Haystack’s design passed with flying colors, with no Requests for Actions (RFAs)!

Shown here is one of the components reviewed in the delta-CDR: the layout of the upgraded VLBI Data Acquisition (VDAQ) board, updated because previously used parts are no longer available. The new board design is a single configuration versus multiple previous ones for all affected systems (which are many).

Most important is that the control and monitoring software that interfaces to all these systems will not have to be modified for this upgrade. And this is just one of many improvements in the new design. Congratulations to the entire team on achieving this successful review!


JULY 26, 2023

A round metal disk with a large hole in the middle and indentations carved out around the rim
Updated with actual photograph (hand, and hand sanitizer, for scale)!
Round blueprint of a plate with holes around the edges
The plate is about 20″ in diameter and weighs approximately 12 pounds

Progress continues on the Fortaleza signal chain build! One of the important component categories is the interfaces: pieces that let MIT-built components work together with components built elsewhere. As an example, the manufacturing process is now underway for something called the feed interface plate, which is what the engineers call a “mating plate” that joins the antenna, built by ISI, and the MIT-built feed. The interface between the positioner and the antenna feed cone is an opening and bolt circle to match the upper interface plate of the positioner. Once built, this piece will be shipping to the antenna vendor in early fall for a factory acceptance test (resulting in the unfortunate acronym FAT in systems engineering lingo).

JUNE 2, 2023

The next major milestone in this antenna build project is the Delta CDR, which stands for Critical Design Review, coming up in July. The “delta” means that it covers differences from the previous design used in the McDonald Observatory (MGO) antenna build in Texas. At this Delta CDR, which includes the Haystack, Fortaleza, and NASA teams and takes about half a day, the teams review together any modifications between the previous antenna design and this new and improved one. Potential examples include digital backend changes (next-generation updates and other continuous improvements) and replacements for now-unavailable components.

MAY 11, 2023

One of software engineer Violet Pfeiffer’s contributions to the Fortaleza signal chain is her work on the backend computer. This backend PC is a server that provides data to the R2DBE (ROACH digital backend), which in turn converts the analog baseband signal to a digital signal. This hardware is used in the Fortaleza antenna’s signal chain, where geodetic data is collected and processed in the NASA antennas and others all around the world for the purposes of determining time on earth, allowing the GPS (Global Positioning System) to work and enabling accurate timekeeping of UT1, or universal time, among other things. So make sure to thank Violet (and the many other people involved, of course) for helping make sure we get to the right place on time!

APRIL 20, 2023

This component is 11.3 lbs before weight removal, and 8.6 lbs after weight removal.

One of the interesting background aspects of our capability for improvement in the updated designs possible with successive antenna builds is the increased efficiency achieved by removing as much unnecessary weight as possible from certain components. The front end of the new Fortaleza antenna (everything from where the incoming signal enters to where the signal is separated into two frequency bands, before they are transferred to the back end equipment for processing) will be made lighter by the Haystack engineering system of removing material from machined elements. Even small weight savings can be made in this way, by shelling out or removing material in regions with low mechanical stresses—every little bit adds up and improves performance.

(If you’re interested in explanations of some of the basic technical terms in these posts, stay tuned! A series of future updates will get into definitions that non-scientists and non-engineers will appreciate, along with diagrams and photos.)

APRIL 6, 2023

R2DBEs incoming! We’ll get into some of these technical components in more detail here later, but this week we’re highlighting the contents of the R2DBEs, or ROACH-2 digital backends, five of which are fresh new arrivals at Haystack. These digital backend systems, also used in the Event Horizon Telescope black hole images, digitize and time-stamp the incoming radio signals before they are sent on to other components for recording and analysis.

The basic components inside the R2DBE (ROACH-2 digital backend), part of the Haystack VGOS signal chain design

MARCH 23, 2023

It probably won’t surprise anyone that CAD is used for antenna design: for each new signal chain, the Haystack team examines past CAD diagrams and adapts them with any improvements and updated features we have designed to be incorporated into the new antenna build. The engineering teams are also reviewing the parts list in great detail and noting significant updates: some of these items have “long-lead” schedules and must be ordered very early in the process. The team is also working on compressor updates, based on analysis of past compressor performance. In addition, the R2DBEs, which are “digital back-end” systems that digitize and time-stamp the radio signals before sending them on for recording—also used in the Event Horizon Telescope historical imaging of black holes—have been shipped and will arrive at Haystack for later configuration and software installation next week.

Antenna guts

MARCH 9, 2023

Time for a little retail therapy! The purchasing phase is underway. Granted, it’s not the most glamorous step, but this stage is of course crucial to the overall signal chain plan. Early acquisitions include a few high-powered computers and a compressor.

front panel of a radio telescope compressor (from another NASA antenna)

The compressor is an essential piece in a radio telescope’s signal chain: it is part of the cryogenics system, which cools the receiver. By reducing the temperature, the cryogenics system thus minimizes the electromagnetic “noise” that is contributed by components within the signal chain. At these extremely low temperatures—just above absolute zero—the sensitivity of a receiver is significantly increased and incredibly faint astronomical signals can be detected.

MARCH 1, 2023

GOOD TO GO! The build of the NASA SGP Fortaleza radio telescope in Brazil has been launched! So far, the Haystack signal chain design and installation teams have been doing some essential kickoff work, such as figuring out the two-year schedule down to the smallest task and assignments, making sure everyone on the team follows the documentation system and naming scheme for engineering diagrams, and putting in place a shipping system to get components to Brazil, amongst other work. Parts are being ordered and everyone is working on their starting assignments! In this blog, we’ll share their tried-and-true processes and show you what it takes to design, create, and install a top-end signal chain for a NASA radio telescope.