Research and Talks

miniCarb Flight Software

I am currently the software lead for the miniCarb CubeSat mission. We are using Space Plug-And-Play compatible middleware from Space Dynamics Laboratory for the flight software. The work necessary to enable successful mission software involves proper coding and physics configuration for the payload instrument, the attitude control system, GPS, and a number of other subsystems. It has been an incredibly gratifying challenge to get all of these systems doing what they are supposed to do when the satellite is placed in orbit.

Satellite Track Recognition

As a Postdoc I worked on the Space-based Telescopes for Actionable Refinement of Ephemeris (STARE) mission at Lawrence Livermore National Laboratory. It involved launching a pair of 3u CubeSats that were intended to take "up-close" pictures of other satellites and debris in orbit around the earth to refine their orbital ephemeris. This would reduce uncertainty in collisional predictions, thereby reducing the amount of false warnings for impending collisions. My work consisted of writing new algorithms for automatic satellite track recognition, characterizing various visible imagers, and writing the embedded firmware that controlled the optical payload. The following image is an example of an identified satellite track along with the positions predicted by our STARE measurements and calculations compared to the ones predicted by the available TLEs.

LSST H2RG Guider Testing

When I was in graduate school, we set up a laboratory in the Stanford Varian Astrophysics Building to do testing for the Large Synoptic Survey Telescope (LSST) guider subsystem. The HyViSI H2RG was used with a laser spot projection system to do centroid accuracy measurements as a function of clocking frequency and star brightness. The hybrid CMOS design is well suited for guiding since the same frame rate can be obtained for a star independent of its location on the detector.

Hybrid CMOS H4RG Detectors

In graduate school I was involved in an effort to test and characterize the Teledyne H4RG 16 MegaPixel HyViSI as a potential sensor for the LSST guider. The H4RG is a Hybrid Visible Silicon (HyViSi) CMOS imager, different from the Charge Coupled Devices (CCDs) usually used in optical astronomy. CMOS imagers present a number of very appealing features for astronomy, such as high speed photometry of stars.

The adjacent image is a picture of M57 taken with the H4RG. It is a combination of 3 minute exposures using G (400-600 nm) and I (670-800 nm) filters.

SIDECAR ASIC Firmware

I have been developing software and assembly code for the SIDECAR ASIC produced by Teledyne Scientific. This is the chip that will replace the control electronics for the Hubble Advance Camera for Surveys (ACS) and control the detectors on board the future James Webb Space Telescope (JWST). I am continually modifying the microcontroller assembly code to acheive better noise performance and implement additional functionality such as onboard centroiding. If you are an astronomer that is using this chip and would like a distribution of the code, please email me.

LSST Cosmic Ray Simulations

An early project I undertook in graduate school was to model cosmic ray events in the LSST detectors with the GEANT4 software package. The purprose was to identify and characterize the events in each frame while also trying to understand their origin. And more importantly, it was try to figure out how to separate cosmic rays from fast transient celestial events such as stellar flares.

Eventually, the simulations were compared to data from existing large aperture telescopes. Many aspects were modeled well, but a lot of the intricacies of the events remained elusive in the simulations.

Sonic Crystals

Sonic crystals are a subset of a larger cateogry of materials called phononic crystals. These objects have great potential in applications such as sonic wave guides, filters, and focusing sound with a negative index of refraction.

I wish I could say that I currently study these. Unfortunately, I was limited to studying them for my qualifying exam. I managed to do some simulations of these materials using the multiple scattering and plane wave expansion methods.

Publications

The following is a list of the publications I have taken part in during my career. There is a chance that some of the links will break, so if you'd like a copy of one of these papers and can't get it, just email me.

Gaussian Mixture Models as Automated Particle Classifiers for Fast Neutron Detectors, B. Blair, C. Chen, A. Glenn, A. Kaplan, J. Ruz, L. Simms, R. Wurtz, Statistical Analysis and Data Mining: The ASA Data Science Journal, July 25, 2019

Pulse Discrimination with a Gaussian Mixture Model on an FPGA, L. Simms, B. Blair, J. Ruz, R. Wurtz, A. Kaplan, A. Glenn, Nuclear Inst. and Methods in Physics Research, A, Volume 900, p. 1-7, 21 Aug. 2018

Methodology and Performance Comparison of Statistical Learning Pulse Shape Classifiers as Demonstrated with Organic Liquid Scintillator, R. Wurtz, B. Blair, C. Chen, A. Glenn, A. Kaplan, P. Rosenfield, J. Ruz, L. Simms, Nuclear Inst. and Methods in Physics Research, A, Volume 901, p. 46-55, 1 Sep. 2018

Government-owned CubeSat Next Generation Bus Reference Architecture, V. Riot, L. Simms et al., TS5, Aug. 7, 2013

Orbit Refinement with the STARE Telescope, L. Simms et al., Journal of Small Satellites, Vol. 2, No.2, pp. 235-251, Dec. 2013

The Space-based Telescopes for Actionable Refinement of Ephemeris Mission, V. Riot, W. De Vries, L. Simms et al., SSC13-XI-11, Aug. 16, 2013

CXBN: A Blueprint for an Improved Measurement of the Cosmological X-Ray Background. L. Simms et al., Proc. SPIE, Vol 8507-44, Aug 15, 2012

The Cosmic X-Ray Background NanoSat (CXBN): Measuring the Cosmic X-Ray Background using the CubeSat Form Factor, K. Brown et al., Proceedings of the AIAA/USU Conference on Small Satellites, SSC12-VII-6, Aug 12, 2012

Space-based telescopes for actionable refinement of ephemeris pathfinder mission, L. Simms, W. De Vries, V. Riot, S. Olivier, A. Pertica, B. Bauman, D. Phillion, S. Nikolaev, SPIE Optical Engineering, 51, Jan 19, 2012

Analysis of Galaxy 15 Satellite Images from a Small-Aperture Telescope. S. Nikolaev, D. Phillion, L. Simms, A. Pertica, S. Olivier, R. Cognion, Proceedings of the Advanced Maui Optical and Space Surveillance Technologies Conference, Sep 13-15, 2011

Autonomous SubPixel Satellite Track Endpoint Determination for Space-Based Images, L. Simms, Applied Optics, 50, 22, D1-D6, 2011

Optical Payload for the STARE Pathfinder Mission, L. Simms, V. Riot, W. De Vries, S. Olivier, A. Pertica, B. Bauman, D. Phillion, S. Nikolaev, Proc. SPIE Defense and Security, 8044-05, 2011

Hybrid CMOS SiPIN Detectors as Astronomical Imagers, Lance Simms, PhD Thesis, Stanford University, October 2009.

Performance studies of the CMS Strip Tracker before installation, W. Adam et al., Journal of Instrumentation, Vol. 06, 4 P06009, June 2009.

Stand-alone cosmic muon reconstruction before installation of the CMS silicon strip tracker, CMS Tracker Collaboration, Journal of Instrumentation, Vol. 06, 4 P05004, May 2009.

Telescope Guiding with a HyViSI H2RG Used in Guide Mode, L. Simms, D. F. Figer, B. J. Hanold, S. M. Kahn, D. K. Gilmore, Proc. SPIE, Vol. 7439, 2009.

First use of a HyViSI H4RG for astronomical observations, L. Simms, D. F. Figer, B. J. Hanold, D. J. Kerr, D. K. Gilmore, S. M. Kahn, J. A. Tyson, Proc. SPIE, Vol. 6690, 2007.

Testing and Operation of the SIDECAR ASIC for DUNE and LSST, L. Simms, S. M. Kahn, D. K. Gilmore, S. Seshadri, Technical Report for NASA/JPL, July 2008

Studies of Atmospheric Turbulence and its Effect on Image Ellipticity, L. Simms, D. Burke, SLAC preprint.

Talks and Presentations

Here are some of the talks and presentations I've given. Some of them are meant to have embedded movies, which are also included below.

Press

I can't say that I've received any press worth bragging about for the work that I've done. But here are a few articles to summarize some of the work highlighted above in less technical terms.