Srikrishna's Research

Curriculum Vitae & Publications [PDF]

Research Statement [PDF]

Optical Instrumentation
ARGOS

ARGOS is an multi laser-guide star ground layer adaptive optics system for the LBT. It consists of a constellation of three greeen laser star per each of the "eyes" of the binocular telescope. A further upgrade will be a fourth sodium laser based star to create a hybrid AO system that uses stars at 12km (green) and 80km (yellow) to do a more comprehensive AO correction.

The primary client instrument for ARGOS is LUCIFER, a near-infrared imager with spectroscopic capabilities in seeing- and diffraction limited modes with multi-object spectroscopic capability. ARGOS will provide near-diffraction-limited optical quality over the 4'x4' field of LUCIFER (in K-band) with the green lasers and a diffraction-limited optical quality when upgraded with the additional sodium lasers.

Here is a conference paper(pdf) describing the laser system part of the project and the accompanying poster(jpg).


Infrared Instrumentation
FanCam

FanCam is an NSF-funded Near-Infrared Camera built for the 31-in telescope at the Fan Mountain Observatory. It was built at the Virginia Astronomical Instrumentation Lab under the supervision of Mike Skrutskie and John Wilson. I and Chan Park performed the optical, mechanical and cryogenic design and assembly.

FanCam instrument specs can be found here. A poster made by Chan and me describing FanCam is here. The instrument and its observations have already contributed to four PhD thesis projects, numerous undergraduate theses as well as undergraduate research at other universities.


ISSSpec

ISSSpec is a space-qualified hand-held near infrared slit spectrograph for Earth observations based on a commercial InGaAs camera. It was commissioned by Dr. Greg Olsen(the third space tourist) to be used on the International Space Station during his week-long trip in October 2005. I lead the instrument design, assembly and testing.

It was designed, and three copies built, with a budget of less than $5000 in under four months using off-the-shelf optics. It was certified space-qualified in Russia and one copy was flown to the ISS. UVa has retained one copy that is used for demonstrations.

Here is a conference paper(pdf) describing the instrument and the accompanying poster(jpg).



InGaAs Detector Development

The University of Virginia, in collaboration with Sensors Unlimited, Inc.(a subsidiary of Goodrich Corp.) has been developing Indium-Gallium-Arsenide (InGaAs) detectors for ground-based astronomical applications. Since InGaAs fabrication techniques are less costly than HgCdTe, such detectors have the potential to be more economical than HgCdTe arrays and expand opportunities for infrared astronomical observations for small observatories.

This NSF-funded project has lead to the development of a 2.34 micron cutoff low dark current InGaAs array that will be installed in CorMASS in the near future to demonstrate the detector's capabilities. I have worked on testing and characterization of all the detector diodes and arrays involved in this project. Here are two conference papers(pdf1,pdf2) and the accompanying posters(jpg1,jpg2) on this project.


TripleSpec

Triplespec is an R ~ 3600 cross-dispersed near-infrared spectrograph in the spectral range of 0.9-2.4μm. University of Virginia has collaborated with Cornell, JPL and CalTech to design and build three nearly identical copies of TripleSpec for use at various large telescopes. I lead the design of the mechanical mounting for the slitviewer optics and detector for all three instruments.

Science

A sample of OJ287 observations(Stokes parameter Q)
NIR Short-Periodic Variability of OJ 287

OJ 287 is one of the most extensively studied Blazars, and exhibits complex variability at all wavelengths and virtually at all timescales. However, periodic variability in this object is elusive on most timescales, with the only stable periodicity detected being the 2-year separated flares that repeat every 11.6 years. There have been multiple detections in radio observations for nearly 25 years of various transient periodicities on 15-30 minute timescales at multiple radio frequencies. A detection of a corresponding intermittent NIR variability, either photometrically or polarimetrically will help better characterize the processes in accretion disks and jets that lead to variability. I have undertaken a two year observational project with FanCam to search for such a variability and also to demonstrate the capabilities of FanCam with regard to long-term multi-epoch variability studies.


A power spectrum of the data sample shown on the left
NIR Variability in the Embedded Clusters NGC1333 & NGC7129

This project, lead by my close collaborator Chan Park, involves near-infrared photometric monitoring of the embedded clusters NGC 1333 and NGC 7129. Using FanCam, we have obtained photometric data in J, H & Ks bands on one 8'x8' field in NGC 7129 and two fields in NGC 1333 at more than 30 epochs over the time period of November 2005 to October 2007. Chan has detected and categorized a significant number of new Class I and Class II YSOs in these clusters. We are currently analysing the data to shed light on the physical processes behind the observed variability.