Always dream and shoot higher than you know you can do. Do not bother just to be better than your contemporaries or predecessors. Try to be better than yourself.

William Faulkner

















Raj: " Six months ago, my research testing the predicted composition of trans-Neptunian objects ran into a dead end."


Leonard: "So, wait, what have you been doing for the past six months?"

Raj: "You know, checking e-mail, updating my Facebook status, messing up Wikipedia entries"  

The Big Bang Theory




You may write me down in history

With your bitter, twisted lies, You may trod me in the very dirt

But still, like dust, I’ll rise.

Maya Angelou




In theory, there is no difference between practice and theory. In practice, there is.


Research Interests


Stellar occultations

Stellar occultations, or the light from a star being blocked as it passes behind a foreground object, provide significant information on bodies in the outer solar system. Observations of these events offer some of the highest spatial resolution data that is achievable from Earth (on the order of a few km at Pluto). Therefore, stellar occultations are employed to determine planetary diameters and to probe the temperature and pressure profiles of planetary atmospheres. These events can also lead to the discovery of features such as satellites, rings, and atmospheres.

During a stellar occultation, the shadow created on the Earth is a function of the size of the body and its distance from the Earth. For the objects in which we are interested (particularly Pluto & Charon and trans-Neptunian objects), the shadow is significantly smaller than the Earth's angular diameter. An observer must thus be in the right place at the right time to see the occultation. My colleagues at MIT spend considerable time and effort taking observations and performing astrometry (measuring object and star positions) in order to predict these events. We then use specific instruments to observe the events, including portable CCD camera systems that can be taken all over the world and attached to telescopes that are located in the predicted shadow path.

Successful observations include stellar occultations by Pluto from 1988 to present, Pluto's moon Charon, 55636, Quaoar, Chiron, and Sedna. These observations have allowed us to place important physical constraints on large TNOs, in order to determine object diameters and search for binaries and atmospheres. In the case of Pluto, the observations have allowed us to monitor the evolving and dynamic atmosphere, and have served as metrics for atmospheric models. Please see the publications page for more details about my research involving stellar occultations and modeling Pluto's atmosphere.


Trans-Neptunian objects (TNOs)

The trans-Neptunian objects are small icy, rocky bodies having orbits at and beyond that of Neptune. The trans-Neptunian region is likely the least thermally modified area of the Solar System and thus may contain a primordial population of bodies. This is important because objects that are remnants from earlier times provide insight into the formation and evolution of the Solar System. In addition, TNOs provide clues for understanding planetary formation processes that are occurring around other stars. The Pluto system, discovered decades before other TNOs, is located in the Kuiper Belt (a subset of the trans-Neptunian region, spanning ~30-50 AU) and specifically in a 3:2 orbital resonance with Neptune.

My colleagues and I have studied TNOs by searching for new objects (as part of the Deep Ecliptic Survey) and performing dynamical analyses. Investigation of the survey results has allowed us to identify different dynamical classes of TNOs and to determine parameters such as the distribution of orbital inclinations and the derived total popultation of objects for various classes. We have also investigated the relationship between TNO orbital dynamics and color, through photometric observations with the 6.5-m Magellan telescopes at Las Campanas Observatory. For more details, please see my publications.



Dusty plasmas

Evidence of dust dynamics near surfaces in the Solar System ranges from particles levitating above the lunar horizon observed by the Surveyor spacecraft, to spokes in Saturn's rings, to dust ‘ponds’ on asteroid Eros. Such dust dynamics are most likely the result of interactions between charged dust particles and plasma sheaths above planetary surfaces.

My thesis work involved experimental investigations of dust charging and dynamics near surfaces with sheaths and related the results to environments on the Moon, Eros, and Mercury. I have a continuing interest in dust dynamics near the surfaces of bodies in the Solar System, particularly the Moon and asteroids. For additional details, please see my publications on dust dynamics and/or the Univ. of Colorado's dusty plasma group.




Occultation observations require high-cadence, low-deadtime, accurately-timed, high-quality images. Instruments capable of these requirements are not readily available on telescopes around the world; therefore, I have been involved in building such instruments.

At the SAAO, I lead the project to build SHOC (Sutherland High-speed Optical Cameras). I supervised an MSc student who commissioned these cameras in 2013. SHOC was based on a similar instrument, MORIS (MIT Optical Rapid Imaging Systems), that I built for NASA's 3-m Infrared Telescope Facility (IRTF) on Mauna Kea, Hawai'i in 2011. In 2005, with my colleagues at MIT and Williams College, I was involved in building the Portable Occultation, Eclipse, and Transit Systems (POETS). Each of these systems (SHOC, MORIS, and POETS) consists of a high-speed camera, an instrument control computer, and a GPS to trigger frames and establish accurate timing and location. In the case of POETS, all of the components can be transported as carry-on luggage. The cameras contain back-illuminated CCDs, with > 90% quantum efficiency, ~6 electrons read noise, better than microsec timing accuracy, and only a few msec deadtime during frame transfer.

We have deployed POETS with great success for such events as the 18 March 2007 occultation of P445.3 by Pluto observed from the southwestern U.S., the 12 June 2006 occultation by Pluto of P384.2 observed from Australia and New Zealand, and the 11 July 2005 occultation of C313.2 by Charon observed from South America. SHOC and MORIS have been used to observe stellar occulations by Pluto, Chiron, 55636, and other TNOs. In addition, as facility instruments, SHOC and MORIS are being employed by other astronomers for projects such as extrasolar planet transits and imaging of Near-Earth asterids.

Please see the publications page for instrument papers describing POETS, MORIS, and SHOC.