Some EDI Literature

May 2017

Recent documents from our UC Berkeley/LLNL group

31. “Spectral resolution boosting Gemini Planet Imager’s Integral Field Spectrograph using a small Externally Dispersed Interferometer addition”

D. J. Erskine, briefing, GPI 2.0 Mtg, Stanford Univ., March 9, 2017, host Prof. Bruce Macintosh. Erskine-SpecResBoostingGPI.pdf

Briefing for GPI folks considering possible upgrades. Showed how adding 0.6 cm interferometer to integral field spectrograph boosts R=40 to effectively R=4000 for atmospheric features.

30. “Glasses for Mr. Magoo’s Spectrograph”

D. Erskine, Astronomy Beat, newsletter for Astr. Soc. Pacific, edited by L. Shore, vol. 154, p1-7, March 8, 2017. AstroBeatGen.pdf

History and photos of EDI over the years, written for a nonscientist audience

29. “Greatly enhanced exoplanet biosignature from an interferometer addition to a low resolution spectrograph”

D. J. Erskine, P. S. Muirhead, A. M. Vanderburg, A. Szentgyorgyi, AAS meeting, Austin, TX, June 4-8, 2017, poster 118.07. Poster2017AAS.pdf

Poster for AAS meeting, Austin TX, June 4-8, 2017. Modeling shows adding 0.6 cm interferometer to Gemini Planet Imager boosts R=70 to effectively R=4000 for detecting atmospheric spectral features

28. Chapter: "Dispersed Interferometers” in Book: “The WSPC Handbook of Astronomical Instrumentation”

David J. Erskine, World Scientific Publishing Company, Editors: David Burrows and Anna Moore, early 2017. WorldSciGen.pdf

Invited review article describes apparatus and sample data of three dispersed interferometer techniques: externally dispersed interferometry (EDI & DFDI), spatial heterodyning spectroscopy (SHS & HHS), and dispersed Fourier transform spectroscopy (dFTS).

27. “High-resolution broadband spectroscopy using externally dispersed interferometry at the Hale telescope: Part 2, photon noise theory”

D.J. Erskine, J. Edelstein, E. Wishnow, M. Sirk, P.S. Muirhead, M.W. Muterspaugh, and J.P. Lloyd, J. Astr. Tele. Instrm. Sys. 2(4), 045001 (2016). TediTenxPart2gen.pdf

Part2. Describes photon noise theory for EDI spectroscopy especially with multiple delays. Numerical simulations demonstrate that fringing and nonfringing noise components are uncorrelated, and EDI can improve upon photon SNR of conventional spectrograph at low boosts. At high boosts EDI has similar SNR as conventional spectrograph with proportionately reduced slitwidth to achieve the high resolution, but without the focal lens blur or pixel Nyquist limitations.

26. “High-resolution broadband spectroscopy using externally dispersed interferometry at the Hale telescope: Part 1, data analysis and results”

D.J. Erskine, J. Edelstein, E. Wishnow, M. Sirk, P.S. Muirhead, M.W. Muterspaugh, J.P. Lloyd, Y. Ishikawa, E. McDonald, W. V. Shourt, A. M. Vanderburg, J. Astr. Tele. Instrm. Sys. 2(2), 025004 (2016). TediTenxPart1gen.pdf

Part1. Comprehensive description of data analysis, results, instrument noise analysis. Notable: discovery of a data analysis method that further reduces sensitivity of final PSF wavelength shift to wavelength shift insults, from 20x to 350x, by overlapping adjacent delay peaks. This allows EDI to produce high res spectrum in spite of extremely large and irregular PSF shifts of the native TripleSpec. See Sects. 9 & 10.

25. “Dramatic robustness of a multiple delay dispersed interferometer to spectrograph errors: how mixing delays reduces or cancels wavelength drift”

D. Erskine, J. Edelstein, A. Kim, E. Linder, J. Lloyd, P. Muirhead, M. Sirk, E. Wishnow, SPIE Astron. Tele. Instrum., Edinburgh, UK, June 26 - July 1, 2016, Ground-based Airborne Instrum. for Astron. VI, proceedings & poster 9908-224. EdinburghSPIEgen.pdf and 37x37PosterErskineGen.pdf

Conference proceedings and poster describe the new crossfading method for eliminating PSF wavelength drift by mixing delay pairs.

24. “Giving Cosmic Redshift Drift a Whirl”

Alex G. Kim, Eric Linder, J. Edelstein, and D.J. Erskine, Astropart. Phys. 62, pp. 195-205 (2015). CosmicWhirlAstroPart2015.pdf

Theory paper considers using an EDI or SHS for measuring very tiny long term changes in velocity caused by cosmic expansion.

23. “High Resolution Broad-Band Spectroscopy in the NIR Using the TripleSpec Externally Dispersed Interferometer at the Hale Telescope”

D.J. Erskine, J. Edelstein, M. Sirk, E. Wishnow, Y. Ishikawa, E. McDonald, W. V. Shourt, SPIE Astr. Tele. & Instr., Montreal, June 22-27, 2014, paper 9147-42. Montreal2014_SPIE.pdf

Briefly summarizes data processing algorithm for wide bandwidth 4x to 10x resolution boosting of NIR spectrograph at Mt. Palomar 5m telescope. Highlights include eliminating ringing, calibration of glass dispersion, and diagrams of new visible light EDI under construction.

22. "Measuring Precision Wideband Stellar Spectra using a Dispersed Interferometer"

D. Erskine, J. Edelstein, M. Sirk, A. Vanderburg, and E. Wishnow, Opt. Soc. Am. Conf. on Fourier Transform Spectroscopy, Arlington, VA, June 23-27, 2013. FTS_abstr_Arlington_2013.pdf

Automated the software and calibrated the glass delay dispersion so that spectral reconstruction can be computed rapidly across the whole bandwidth of native spectrograph, without manual tweaking of phasing.

21. "Enhanced spectral resolution via externally dispersed interferometry"

J. Edelstein, D. J. Erskine, M. Sirk, A. Vanderburg, E.H. Wishnow, Grnd-based & Airbrn. Instr. Astr. IV, July 1-6, 2012, Amsterdam, Netherlands, SPIE 8446, paper 177, (2012). edi_spie2012c2.pdf

Work in progress on the topic of resolution boosting using TEDI data.

20. "Ten-fold Spectral Resolution Boosting using TEDI at the Mt. Palomar NIR Triplespec Spectrograph"

D.J. Erskine, Jerry Edelstein, P. Muirhead, M. Muterspaugh, K. Covey, D. Mondo, A. Vanderburg, P. Andelson, D. Kimber, M. Sirk, J. Lloyd, SPIE 8146, “UV/Optical/IR Space Tele. & Instr.: Innovat. Techn. Cncpts V”, Aug. 21-25, 2011, San Diego, CA, paper# 8146-22. Ten-fold18b-IM.pdf

Preliminary description of resolution boosting on TEDI. 10x is the highest achieved boosting ratio to date on starlight (the previous high res results were in the lab and on iodine not starlight).

19. "Precise Stellar Radial Velocities of an M Dwarf with a Michelson Interferometer and a Medium-Resolution Near-Infrared Spectrograph"

Philip S. Muirhead, Jerry Edelstein, David J. Erskine, Jason T. Wright, Matthew W. Muterspaugh, K. R. Covey, E. Wishnow, K. Hamren, P. Andelson, D. Kimber, T. Mercer, S. Halverson, A. Vanderburg, D. Mondo, A. Czeszumska and J. P. Lloyd, PASP 123, pp 709-724, June (2011). TEDI_PASP2011.pdf

Comprehensive peer-reviewed paper describing TEDI 2.0 Doppler measurement results. Derived from Phil Muirhead's thesis work.

18. “Precise Infrared Radial Velocimetry with the Triplespec Exoplanet Discovery Instrument: current performance and results”

P. Muirhead, J. Edelstein, J. Wright, D. Erskine, M. Muterspaugh, K. Covey, M. Marckwordt, S. Halverson, M. Marckwordt, D. Mondo, J. Lloyd, Grnd-based & Airbrn Instr. Astr. III, June 27 - July 2, 2010, San Diego, CA, SPIE 7735, p77357X (2010). L7735_SPIE_Muirhead2010b.pdf

While TEDI version 2.0 was finished construction in the lab, it hadn't been installed at the telescope yet, so this paper analyzes TEDI version 1.0 problems. Key to redesigning version 2.0 was a good understanding of issues raised by 1.0 and how to address them.

17. “Infrared Radial Velocimetry with TEDI: Performance Development”

J. Edelstein, P. Muirhead, J. Wright, K. Covey, D. Erskine, M. Muterspaugh, J. Lloyd, S. Halverson, M. Marckwordt, D. Mondo, Grnd-based & Airbrn Instr. Astr. III, June 27 - July 2, 2010, San Diego, CA, SPIE 7735, p773583 (2010). 7735_SPIE_Jerry2010.pdf

Describes some of the growing pain problems with version 1.0 and our design for version 2.0 which will address those issues.

16. "Dispersed interferometer for Doppler planet search at Mt. Palomar 200 inch Telescope"

D.J. Erskine, J. Edelstein, E. Wishnow, J. Lloyd, P. Muirhead, J. Wright and M. Muterspaugh, OSA/Fourier Transform Spectroscopy, Vancouver, Canada, April 26-30, 2009. FTS_Van5b.pdf

Abstract for a conference that i ended up not being able to attend. Useful for showing some early TEDI raw data. Unpublished.

15. "Dispersed Interferometry for Infrared Exoplanet Velocimetry"

J. Edelstein, D.J. Erskine, J. Lloyd, M. Muterspaugh, P. Muirhead, and J. Wright, Astron. Telescopes & Instrum., Marseille, France, June 23-28, 2008, SPIE 7014 (2008). Marseille_SPIE7014-274.pdf

Shows first-light raw data (spectra with fringes) of TEDI

14 "Externally Dispersed Interferometry for Precision Radial Velocimetry"

D.J. Erskine, M. Muterspaugh, J. Edelstein, J. Lloyd, T. Herter, W.M. Feuerstein, P. Muirhead, and E. Wishnow, AAAC Exoplanet Task Force White Paper, Amer. Astron. Soc. 211th Mtg., Austin, TX, Jan. 7-11, 2008, <2007arXiv0710.2130E>. ExoPTF9c_.pdf

White paper written for Exoplanet Task Force. Nice summary of theoretical arguments for using EDI in future Doppler planet surveys, especially of cool stars.

13. "TEDI: the TripleSpec Exoplanet Discovery Instrument"

J. Edelstein, M.W. Muterspaugh, D.J. Erskine, W.M. Feuerstein, M. Marckwordt, E. Wishnow, J. Lloyd, T. Herter, P. Muirhead, G. Gull, C. Henderson, S. Parshley, Techn. and Instr. Detect. Exoplanets III, San Diego, Aug 27-31, 2007, Proc. SPIE 6693 (2007). TEDI_SPIE6693b.pdf

Plans (drawings etc) for the interferometer being built to fit inside the Cassegrain output hole of Mt. Palomar 200 inch telescope mirror.

12. "The TEDI Instrument for Near-IR Radial Velocity Surveys"

J. Edelstein, D. Erskine, J. Lloyd, T. Herter, M. Marckwordt, and M. Feuerstein, SPIE 6269, Orlando FL, May 2006. Tedi.spie.06c.pdf

Briefly summarizes the interferometer portion of the TEDI project, which is to place a Doppler interferometer at Mt. Palomar 200 inch in series with Cornell's TripleSpec near-infrared spectrograph, to search for planets around cool stars.

11. "Noise Studies of EDI for Doppler Velocimetry"

D.J. Erskine, J. Edelstein, J.P. Lloyd, and P. Muirhead, SPIE 6269, Orlando FL, May 2006. OrlandoNoise17pp2.pdf

Describes mathematical methods for calculating EDI and conventional photon-limited velocity noise, given any arbitrary stellar spectrum. Examples given for a T=1600 star in the near infrared, with various rotational blurring.

10. "High Resolution Absorption Specroscopy using Externally Dispersed Interferometry"

J. Edelstein & D. Erskine, in Optics & Photonics, Proc. SPIE 5898 (2005). UVDiego5.pdf

Describes advantages of using EDI for high resolution absorption spectroscopy, such as for UV-observing space missions

9. "Externally Dispersed Interferometry for Planetary Studies"

D. Erskine & J. Edelstein, in Optics & Photonics, Proc. SPIE 5905 (2005). TediDiego7.pdf

Plan to measure Doppler velocities of cool stars by combining an EDI with Cornell's TripleSpec IR spectrograph at Mt. Palomar Observatory

Older documents from the LLNL / UC Berkeley group

8. "Interferometric Resolution Boosting for Spectrographs"


D. Erskine & J. Edelstein, in Astronomical Instrumentation, Proc. SPIE 5492 (2004)

Demonstration of 6-times boost in spectral resolution, measuring iodine in a benchtop linear spectrograph

7. "High Resolution Broadband Spectroscopy using an Externally Dispersed Interferometer"


D. Erskine, J. Edelstein, W. M. Feuerstein & B.Welsh, Astrophys. Jrnl. Lett. 592, L103-L106, Aug. 1, 2003

Demonstration of resolution boosting effect on Lick Obs. echelle spectrograph using alpha-Virgo, and on a linear grating using sunlight.

6. "Spectral Astrometry Mission for Planets Detection"


D. Erskine & J. Edelstein, in Astronomical Telescopes and Instrumentation, J. Angel, ed., Proc. SPIE 4852 (2003)

Demonstration of spectral astrometry, where the angular difference between two or three stars can be made without requiring a rigid baseline, by counting beats in broadband fringes.

5. "High- resolution Broadband Spectral Interferometry"


D. Erskine & J. Edelstein, in Astronomical Telescopes and Instrumentation, J. Angel, ed., Proc. SPIE 4854 (2003)

Demonstration of resolution boosting effect on Lick Obs. echelle spectrograph

4. "An Externally Dispersed Interferometer Prototype for Sensitive Radial Velocimetry: Theory and Demonstration on Sunlight"


D. Erskine, Publ. Astr. Soc. Pacific 115, 255-269 (2003)

First-principles theory of EDI operation and Doppler data analysis methods, and demonstration data on sunlight showing 12 m/s lunar component.<Compare theories>. See also Ref. 7 for heterodyning reversal theory, and Ref. 12 for more details on Doppler velocity noise calculation.

3. "An Externally Dispersed Interferometer for Sensitive Doppler Extra-solar Planet Searches"


J. Ge, D. Erskine & J. Rushford, Publ. Astr. Soc. Pacific 114, 1016-1028 (2002)

1st stellar EDI data, at Lick Observatory in Dec. 1999, obtaining ~7 m/s precision.

2c. "Techniques in Broadband Interferometry"

Broadband Intrf Patents4d.pdf

D. Erskine, LLNL Report # UCRL-TR-201695, (2003)

Collection of Erskine's patents, reformatted into journal style to aid readability, describing interferometric techniques using white light and uncollimated beams

2b. "Combined Dispersive/interference Spectroscopy for Producing a Vector Spectrum"


David J. Erskine, US Patent 6,351,307, Filed 2000 Feb. 23, issued 2002 Feb. 26

Externally Dispersed Interferometer for Doppler velocimetry, high resolution spectroscopy, and angular measurements

2a. "Single and Double Superimposing Interferometer Systems"



David J. Erskine, US Patent 6,115,121, Filed 1997 Oct. 31, issued 2000 Sept. 5

Designs, techniques and applications for angle-independent, or field-widened, interferometers using white light. Figs. 28A, B & C show a dispersed interferometer.

1. "Novel Interferometer Spectrometer for Sensitive Stellar Radial Velocimetry"


D. Erskine & J. Ge, in Imaging the Universe in Three Dim.: Astphys. with Adv. Multi-Wvlngth. Imag. Dev., W. van Breugel & J. Bland-Hawthorn, ed., Astr. Soc. Pacific 195, 501 (2000)

Shows EDI 1st prototype and early solar and benchmark data

Errata page: clarifications on errors in EDI Literature

Documents from other groups (very incomplete list)

I. "First Extrasolar Planet Discovered with a New Generation....Instrument"


Jian Ge, J. van Eyken, S. Mahadevan, C. DeWitt et al., ApJ 648, 683-695 (2006)

Paper describes the first exoplanet discovered using an EDI, by the Univ. of Florida group, orbiting HD 102195

H. "First Extrasolar Planet Discovered with a New Generation....Instrument"


Jian Ge, J. van Eyken, S. Mahadevan, C. DeWitt et al., Abstract 191.02, AAS Meeting 207 (2005)

Abstract describes the first exoplanet discovered using an EDI, by the Univ. of Florida group

G. "All Sky Extrasolar Planet Searches with Multi-Object Dispersed Fixed-delay Interferometer in Optical and near IR"


Jian Ge, S. Mahadevan, J. van Eyken, C. DeWitt, J. Friedman, and D. Ren, Proc. SPIE 5492, 711-718, 2004

Plans for a future multi-object EDI at Sloan 2.5m, and results of current EDI at Kitt Peak

F. "Design of a stable fixed delay interferometer prototype for the ET project"


S. Mahadevan, Jian Ge, C. DeWitt, J. van Eyken, and G. Friedman, Proc. SPIE 5492, 615-623, 2004

Detailed theoretical analysis of how to make an angle independent delay using an etalon, and make it stable.

E. "Results from upgrades to the radial velocity instrument, ET, at the KPNO 2.1m"


J. van Eyken, Jian Ge, S. Mahadevan, C. DeWitt, J. Friedman, P. Finnerty, D. Ren, and M. Zugger, Proc. SPIE 5492, 445-451, 2004

Photos and schematic of improved EDI at Kitt Peak

D. "First Planet Confirmation with a Dispersed Fixed-Delay Interferometer"


J. van Eyken, Jian Ge, S. Mahadevan, & C. DeWitt, Astrophys. Jrnl. Lett. 600, L79-L82 (2004).

Detection of exoplanet around 51 Pegasi using EDI technique.

C. "A New Doppler Radial Velocity Machine at Kitt Peak for Extrasolar Planet Searches"


Jian Ge, s. Mahadevan, J. van Eyken, C. DeWitt & S. Shaklan, Kitt Peak Nat. Obsv Newsletter, p31, March (2003)

Detection of exoplanet around 51 Pegasi using EDI technique. Photo of apparatus.

C2. "All Sky Doppler Extrasolar Planet Surveys with a Multi-object Dispersed Fixed-delay Interferometer"


Jian Ge, S. Mahadevan, J. van Eyken, C. DeWitt & S. Shaklan, in Scientific Frontiers in Research on Extrasolar Planets, ASP Conf. Series, ed. D. Deming & S. Seager, 2003

Description of Ge's EDI, current results with it, and plans to connect it to multiple fibers to observe many stars simultaneously.

B. "Erratum: Fixed Delay Interferometry for Doppler Extrasolar Planet Detection"


Jian Ge, Astrophys. Jrnl. Lett. 593, L147 (2003)

Corrects omission, that first-light stellar tests with EDI occurred in 1999 with the LLNL-Erskine instrument, not with the Penn. State instrument in 2001.<comments>

A. "Fixed Delay Interferometry for Doppler Extrasolar Planet Detection"


Jian Ge, Astrophys. Jrnl. Lett. 571, L165-L168, (2002)

Announces the EDI technique as his own?, presents an approximate instrument theory for the Doppler measurement. <Compare theories>

Older historical documents

ee. "Mass producing an efficient NIR spectrograph"

Triplespec Spectrograph Design.pdf

Wilson et al., SPIE 5492, pp1295-1305 (2004).

Describes the Triplespec spectrograph

dd. "Simple Method of Reducing Prismatic Spectra"


Edser, E & Butler, C.P., Philos. Mag. 46, pp. 207-216 (1898)

Early use of a Fabry-Perot interferometer in series with a dispersive spectrograph. Differences with EDI include: a) Fabry-Perot interferometer, not Michelson-- fringes are non-sinusoidal due to multiple reflections inside interferometer cavity; b) angle-dependent delay (not field-widened) restricts use to small delays and point sources.

cc. "Laser interferometer for measuring high velocities of any reflecting surface"


L.M. Barker & R.E. Hollenbach, J. Appl. Phys. 43, 4669-4675 (1972).

Example of a monochromatic (i.e. undispersed) velocity interferometer using a wide-angle Michelson, for measuring velocities of laser illuminated shock physics targets.

bb. "Absolute Astronomical Accelerometry"


P. Connes, AstrPhy. Spc. Sci. 110, 211-255 (1985).

Thorough theoretical analysis of conventional Doppler measurement. Introduction of quality factor Q which calculates photon limited velocity noise obtainable from a given arbitrary spectrum.

aa. "Wide-Angle Michelson Interferometer for Measuring Doppler Line Widths"


R.L. Hilliard and G.G. Shepherd, J. Opt. Soc. Am. 56, 362-369 (1966).

Example usage of a wide-angle Michelson, i.e. field-widening, or a superimposing interferometer.

Dave Erskine's scientific publication list

Dave Erskine's scientific bio


David Erskine
Lawrence Livermore Nat. Lab.

Jerry Edelstein
Space Sciences Lab., UC Berkeley

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