header photo


Yale Astronomy

2019 Success!

Feb 7, 2019 - Debra Fischer

Woo-hoo!! Over the past month we have improved the instrumental precision from ~1 meter per second to 0.05 meters per second (5 centimeters per second). That is a factor of twenty improvement! The instrument is now locked down and we are moving on to the last challenge: disentangling photospheric velocities from orbital velocities. It may take a few more months, but now that we have such high fidelity data, we will conquer that challenge, too! The Figure below shows what progress looks like: Dec 2018 was a show-stopper; Jan 2019 was another mystery (fiber tangled in agitator) and February is just where we want to be!

The last blog post detailed a big challenge for improving over the state-of-the-art 1 m/s precision: an interference pattern ("beat frequency", fb) between the ~60.046 Hz vibrations in the detector (f1) and 60 Hz flickering of the laser frequency comb (f2). Andy Szymkowiak was the hero in this story - he diagnosed the problem, came up with a solution, then (with advice from the Menlo laser comb team and the Holoeye engineers) he reprogrammed the frequency of the laser comb flickering from 60 Hz to 55 Hz. If you've studied physics, you can calculate that this shift in f1 changes the period of the beat from a show-stopping 6-minute period to an inconsequential 0.1 second period. If you have not studied physics, then this was best said by Francesco Pepe (leading the Geneva team and the pricipal investigator and designer for HARPS and ESPRESSO):

Wow, what you describe is really amazing. This is a problem that is not easy to find. So, if I understand correctly, what you observed is some kind of stroboscopic effect of the LFC intensity modulation by the cooler vibrations...
Wow2. I'm really impressed.

The excitement is palpable among the team members as these results are rolling in. After a few months of anxious persistence, the team is bouyed up with renewed energy. Over the last month, we've been upgrading computers, benchmarking new extraction and cross-correlation codes, polishing up a new telluric removal code by recent Yale grad Christopher Leet, and testing codes for removing noise that comes from the stars, themselves. It is time to begin observing again. Now all we need are beautiful skies over Flagstaff, like the ones in the image below, taken by John Brewer while he was upgrading the computers at the Discovery Channel Telescope (DCT).

Photo at Happy Jack, AZ (near the DCT) by John Brewer (1/31/19).

About Us

Photo from Lowell Observatory

The EXPRES team works on the discovery of planets orbiting stars other than our Sun, or exoplanets.

EXPRES is a next generation spectrograph that aims to break the record on current measurement precision with the goal of detecting small, rocky planets - similar to Earth - orbiting nearby stars. The instrument blends high resolution and extraordinary stability to produce the highest fidelity data. This journey began long ago; our hope is that EXPRES will help humanity to explore the unknowns in the galaxy.

EXPRES is possible thanks to...

BLOG Archive:

Most Recent Post
2018: December, September, July, June, May, April, March.

News about EXPRES:

EXPRES Cast and Crew

  • Deputy Scientist - 100 Earths Project
    • John Michael Brewer
  • Professors
    • Debra Fischer, Astronomy
    • Jessi Cisewski, Statistics
    • Andrew Szymkowiak
  • Research Scientists
    • Colby Jurgenson
    • Tyler McCracken
    • David Sawyer
  • Graduate Students
    • Allen Davis
    • Ryan Blackman
    • Ryan Petersburg
    • Lily Zhao
    • Joel Ong
  • Undergraduate Students
    • Christopher Leet
    • Yonatan Zeff
    • Abby Mintz
  • Collaborators
    • Sally Dodson-Robinson, University of Delaware
    • Lars Buchhave, Danish National Space Institute
    • Gregory Henry, Tennessee State University
  • We Would Like to Expressly Thank
    • Steve Girvin, Yale University
    • Pieter van Dokkum, Yale University
    • Gábor Fűrész, MIT
    • Andy Szentgyorgyi, Harvard
    • Francesco Pepe, Geneva Observatory
    • Matteo Genoni, Brera Astronomical Observatory
    • Giorgio Pariani, Brera Astronomical Observatory
    • Marco Riva, Brera Astronomical Observatory
    • Ben Hardesty, Lowell Observatory
    • Frank Cornelius, Lowell Observatory