| NSF Org: |
AST Division Of Astronomical Sciences |
| Recipient: |
|
| Initial Amendment Date: | August 23, 2014 |
| Latest Amendment Date: | August 23, 2014 |
| Award Number: | 1429015 |
| Award Instrument: | Standard Grant |
| Program Manager: |
James Neff
jneff@nsf.gov (703)292-2475 AST Division Of Astronomical Sciences MPS Directorate for Mathematical and Physical Sciences |
| Start Date: | September 1, 2014 |
| End Date: | August 31, 2017 (Estimated) |
| Total Intended Award Amount: | $300,000.00 |
| Total Awarded Amount to Date: | $300,000.00 |
| Funds Obligated to Date: |
|
| History of Investigator: |
|
| Recipient Sponsored Research Office: |
501 CRESCENT ST NEW HAVEN CT US 06515-1330 (203)392-6801 |
| Sponsor Congressional District: |
|
| Primary Place of Performance: |
501 Crescent Street New Haven CT US 06515-1330 |
| Primary Place of
Performance Congressional District: |
|
| Unique Entity Identifier (UEI): |
|
| Parent UEI: |
|
| NSF Program(s): | Major Research Instrumentation |
| Primary Program Source: |
|
| Program Reference Code(s): |
|
| Program Element Code(s): |
|
| Award Agency Code: | 4900 |
| Fund Agency Code: | 4900 |
| Assistance Listing Number(s): | 47.049 |
ABSTRACT
In the continual effort to obtain better images of objects in the universe, the emphasis has generally been centered on orbiting observatories or ever-larger ground-based facilities with laser correction of atmospheric turbulence. Both are expensive endeavors with physical limitations. A quite different approach, intensity interferometry, has a significant history in radio astronomy, but was last seriously used for the optical regime in the 1970's using the simple detectors available at the time. Dr. E. Horch of Southern Connecticut State University (SCSU) has recognized that today's very sensitive, extremely fast solid-state detectors motivates that the technique be re-examined, as it would offer the possibility of obtaining separations of orbiting binary stars, stellar diameters, and even complete stellar images using a small array of inexpensive, modest-sized telescopes and commercially available instrumentation. Indeed, the SCSU project is being promoted as an activity well-suited to student involvement at a small undergraduate university.
Intensity interferometry for astronomy utilizes the Bose-Einstein correlation of bosons (and therefore photons) to provide information on the angular size of the radiating source. For telescopes with somewhat less than 1-m aperture distributed over the SCSU campus, Dr. Horch predicts that an angular resolution of 0.1 milliarcseconds can be achieved down to a visual magnitude of ~3.5, allowing detailed inspection of about 200 stars. For comparison, the Sun moved to a distance that yields this apparent magnitude would have an angular diameter of 2 milliarcseconds. Moreover, the effect can be monitored in several wavebands simultaneously through the use of Single Photon Avalanche Diode (SPAD) arrays that have quantum efficiencies near 0.5 and time response of ~0.1 nanoseconds, and the data recorded using GPS technology.
Funding for the development of a modern two-telescope prototype of an intensity interferometer array for the optical is being provided by NSF's Division of Astronomical Sciences through its participation in the Major Research Instrumentation program.
PUBLICATIONS PRODUCED AS A RESULT OF THIS RESEARCH
Note:
When clicking on a Digital Object Identifier (DOI) number, you will be taken to an external
site maintained by the publisher. Some full text articles may not yet be available without a
charge during the embargo (administrative interval).
Some links on this page may take you to non-federal websites. Their policies may differ from
this site.
PROJECT OUTCOMES REPORT
Disclaimer
This Project Outcomes Report for the General Public is displayed verbatim as submitted by the Principal Investigator (PI) for this award. Any opinions, findings, and conclusions or recommendations expressed in this Report are those of the PI and do not necessarily reflect the views of the National Science Foundation; NSF has not approved or endorsed its content.
The goal of this project was to build a new-technology intensity interferometer for use in high-resolution astronomy. Intensity interferometry, also known as the Hanbury Brown and Twiss effect, is a technique first used in the 1950s to obtain information of stellar sources based on the weak correlation in the intensity of light received at two telescopes from the same source. The degree of correlation as a function of the distance between the telescopes can be used to obtain ultra-high-resolution image information. It was used in the 1960s and the 1970s to measure the diameters of about three dozen bright stars, but then fell into disuse due to its inherently low signal-to-noise ratio, even when using large telescopes to collect light. However, using current state-of-the-art timing correlators and photon-counting detectors, this project has shown that the technique can be successfully used with relatively small, portable telescopes to detect photon correlations and therefore to measure stellar diameters. The project also pioneered the use of GPS timing cards to make the instrument "wireless," that is, to have photon collection at two independent telescopes each with its own timing correlator. With the GPS cards, timing markers are inserted into the photon data streams, allowing the data from the two stations to be synchronized and properly correlated after the fact. This allows for much larger separation of the stations, and therefore higher resolution information about the source. The interferometer is complete and functioning well.
The instrument can now be used in the observation of binary stars, providing a basis for the determination of ultra-precise stellar masses based on the mutual orbit of the pair, a key measurement in understanding stellar structure and evolution. Intensity interferometry has constant a signal-to-noise ratio with bandpass, so that extremely narrow-band imaging can be accomplished to the same limit as with a wider filter. Therefore, there is much the technique could offer in terms of imaging stellar surfaces at important line wavelengths. This could tell us much more than we currently know about limb darkening, star spots, stellar activity, and stellar rotation. If the technique can be sufficiently mastered, it may also be of future interest in satellite imaging for remote sensing or military applications.
The project involved the training of two undergraduate students and one graduate student. Both undergraduates have gone on to graduate study in science, and the graduate student is now working as a telescope operator at a major observatory. The project has also provided Southern Connecticut State University with the opportunity to prepare to build a robust public observing program with the two 24-inch telescopes used in the interferometer, thereby promoting science education in the New Haven community.
Last Modified: 11/29/2017
Modified by: Elliott P Horch
Please report errors in award information by writing to: awardsearch@nsf.gov.
