Development of A Near-Infrared Development of A Near-Infrared Camera for use at RBOCamera for use at RBO

A Preliminary defense by Andy MonsonA Preliminary defense by Andy Monson

Motivations for Instrumentation ThesisMotivations for Instrumentation Thesis

Develop NIR camera expertiseDevelop NIR camera expertiseCryo-mechanical techniquesCryo-mechanical techniquesElectronics and array performanceElectronics and array performanceCamera control softwareCamera control softwareNIR observational strategiesNIR observational strategies

Demonstrate camera capabilities Demonstrate camera capabilities Synoptic photometry of bright starsSynoptic photometry of bright stars

NIR CharacteristicsNIR Characteristics CMOS detectors using HgCdTe have reached 2048x2048 pixels. CMOS detectors using HgCdTe have reached 2048x2048 pixels.

EXPENSIVE !!! $350,000.00EXPENSIVE !!! $350,000.00 Atmospheric HAtmospheric H22O absorption defines near-infrared bandsO absorption defines near-infrared bands Filters designed to fit in atmospheric windowsFilters designed to fit in atmospheric windows Thermal emission from sky dominates past 2.5 microns and emission from Thermal emission from sky dominates past 2.5 microns and emission from

OH in atmosphere contributes to flux in H bandOH in atmosphere contributes to flux in H band

What are the benefits of the NIR?What are the benefits of the NIR?

Less sensitivity to extinctionLess sensitivity to extinction Less sensitivity to heavy metal abundance Less sensitivity to heavy metal abundance Systematic errors are less by an order of magnitudeSystematic errors are less by an order of magnitude

Buttes Infra-Red CAMera (BIRCAM)Buttes Infra-Red CAMera (BIRCAM)

BIRCAM was developed to gain insight and develop techniques for BIRCAM was developed to gain insight and develop techniques for constructing the mechanics, electronics, and software interfaces for a larger constructing the mechanics, electronics, and software interfaces for a larger camera currently under development at UW. camera currently under development at UW.

BIRCAM is a capable instrument in its own right.BIRCAM is a capable instrument in its own right.

Optical DesignOptical Design IR cameras need internal optics and a IR cameras need internal optics and a

cold stop to prevent thermal cold stop to prevent thermal background from telescope structure background from telescope structure from reaching the detectorfrom reaching the detector

Re-imaging optics folded to fit in the Re-imaging optics folded to fit in the dewar using an Offner relaydewar using an Offner relay

All mirror design reduced cost, low All mirror design reduced cost, low emissivity and no chromatic aberrationemissivity and no chromatic aberration

Designed in ZEMAX to determine Designed in ZEMAX to determine optimum spacingoptimum spacing

Optics BenchOptics Bench

Everything inside the dewar is atEverything inside the dewar is at

-200°C to minimize thermal -200°C to minimize thermal background.background.

Designed to minimize effect of Designed to minimize effect of thermal contraction.thermal contraction.

Allows for each mirror to be Allows for each mirror to be tip/tilted and positioned relative to tip/tilted and positioned relative to each other for alignment.each other for alignment.

The filter wheel (from BABE) The filter wheel (from BABE) mounts to the bench.mounts to the bench.

A cryo-conditioned stepper motor A cryo-conditioned stepper motor moves the filter wheel via LabView moves the filter wheel via LabView GUI.GUI.

Micro-switches sense the position Micro-switches sense the position of the filter wheel mechanically.of the filter wheel mechanically.

Detector Fanout-BoardDetector Fanout-Board Provided by John Geary (CfA/Harvard)Provided by John Geary (CfA/Harvard) Seats the H2 array in ziff socket and fans out Seats the H2 array in ziff socket and fans out

signal lines from each quadrant to connectorsignal lines from each quadrant to connector Heaters and temperature sensor allow for Heaters and temperature sensor allow for

temperature control of the detector. temperature control of the detector. Enables use of off-chip amplifiers for each of Enables use of off-chip amplifiers for each of

the 32 channels the 32 channels 128 signals to / from the board to the 128 signals to / from the board to the

outside. Wire as fine as hair used for all outside. Wire as fine as hair used for all detector signals. detector signals.

BIRCAM InteriorBIRCAM Interior Fanout-board is spring loaded and Fanout-board is spring loaded and

referenced to optical bench referenced to optical bench Optics bench mounts to cold plate Optics bench mounts to cold plate

and squares detector to the optical and squares detector to the optical axisaxis

Cold straps facilitate coolingCold straps facilitate cooling CaF2 window protects array.CaF2 window protects array. Temperature sensors on optics Temperature sensors on optics

bench monitor temperaturebench monitor temperature

Pre-amp & Array ControllerPre-amp & Array Controller

GUMP is a 32 channel, pre-amplifier GUMP is a 32 channel, pre-amplifier for providing 5x gain from fanout for providing 5x gain from fanout board to controller (IRLABS). Added board to controller (IRLABS). Added resistors to each channel to resistors to each channel to reference ground.reference ground.

Controller electronics (Leach / ARC) Controller electronics (Leach / ARC) provides all voltages to array and provides all voltages to array and converts analog signal from GUMP converts analog signal from GUMP to digital signal to computer. to digital signal to computer. Replaced current limiting resistors to Replaced current limiting resistors to supply adequate power to GUMP supply adequate power to GUMP and the array and the array

Ground for the controller is isolated Ground for the controller is isolated from the power supply (different from the power supply (different chassis). Huge floating ground chassis). Huge floating ground problem eliminated by supplying problem eliminated by supplying isolated ground from GUMP power isolated ground from GUMP power supply. supply.

Signal ChainSignal Chain Developed MultiSim model of signal chain. Developed MultiSim model of signal chain.

Allowed simulation of signal chain Allowed simulation of signal chain Verification of array performance Verification of array performance

Output Waveforms of H2Output Waveforms of H2 0V(full well) to 0.4V(no 0V(full well) to 0.4V(no

light) output from the light) output from the detector/fanout-board detector/fanout-board

GUMP applies -3.7V DC GUMP applies -3.7V DC offset and 5x gainoffset and 5x gain

Controller applies inverting Controller applies inverting gain of 5x and A/D offset.gain of 5x and A/D offset.

Integrator applies Integrator applies (t/RC)=0.5 gain to 16bit A/D(t/RC)=0.5 gain to 16bit A/D

A/D input = -2.5V(full well) A/D input = -2.5V(full well) to +2.5V(no light) to +2.5V(no light)

Gain = 82,800e/65,536ADU Gain = 82,800e/65,536ADU = 1.26e/ADU (theory)= 1.26e/ADU (theory)

Camera and Electronics Work!

Verification and TestingVerification and Testing Bare CMOS multiplexer provided by Rockwell Bare CMOS multiplexer provided by Rockwell

/ Teledyne for testing/ Teledyne for testing Safely verify the electronicsSafely verify the electronics Adjust voltages for 32 independent channelsAdjust voltages for 32 independent channels Adjust bias and offset voltages to tune gain to Adjust bias and offset voltages to tune gain to

fit dynamic range of the A/D converters. fit dynamic range of the A/D converters. Create subroutines to reconstruct (de-Create subroutines to reconstruct (de-

interlace) the 32 channels to form an image. interlace) the 32 channels to form an image.

BIRCAM in CleanroomBIRCAM in Cleanroom BIRCAM during final assembly in BIRCAM during final assembly in

the Cleanroom the Cleanroom Clean all surface of fingerprints Clean all surface of fingerprints

and other volatiles to minimize and other volatiles to minimize outgases in a vacuum outgases in a vacuum

Prevent dust and particulate Prevent dust and particulate matter from contaminating the matter from contaminating the inside. inside.

Hawaii-2 HgCdTe Detector ArrivesHawaii-2 HgCdTe Detector Arrives

2048 x 2048 array (Rockwell / 2048 x 2048 array (Rockwell / Teledyne)Teledyne)

18 micron pixels18 micron pixels CMOS HgCdTeCMOS HgCdTe Full Well 84,000e-Full Well 84,000e- 4 independent quadrants4 independent quadrants Capable of 32 channel read-Capable of 32 channel read-

out (8 per quad)out (8 per quad) Read out time ~1.3sRead out time ~1.3s QE of 0.85, 0.68, QE of 0.85, 0.68,

0.78 at J, H, K0.78 at J, H, K

Wiring for BIRCAMWiring for BIRCAM ~100 ft inside dewar (All done here by myself and electronics shop) ~100 ft inside dewar (All done here by myself and electronics shop) ~1000 ft outside dewar (50% done here by myself and electronics shop)~1000 ft outside dewar (50% done here by myself and electronics shop)

Software for BIRCAMSoftware for BIRCAM Voodoo (Java/C) software modified to Voodoo (Java/C) software modified to

de-interlace the 32 outputs and write de-interlace the 32 outputs and write header information and image.header information and image.

Voodoo configured for Correlated Voodoo configured for Correlated Double Sampling (CDS)Double Sampling (CDS)

Read array (image1)Read array (image1) ExposeExpose Read array (image2)Read array (image2) Net image = image2 - image1Net image = image2 - image1

LabView GUI developed to control LabView GUI developed to control filter wheel position, monitor filter wheel position, monitor temperatures and control detector temperatures and control detector temperaturetemperature

Cool down at RBOCool down at RBO 30 liters of LN2 brought to RBO 30 liters of LN2 brought to RBO

every 5 days every 5 days It takes about 3 hours to cool the It takes about 3 hours to cool the

array to 78K and an additional 3 array to 78K and an additional 3 hours for the optics bench to reach hours for the optics bench to reach 80K80K

BIRCAM is kept continuously cold BIRCAM is kept continuously cold to be ready at a moments notice. to be ready at a moments notice.

BIRCAM at RBOBIRCAM at RBO

BIRCAM mounts to telescope BIRCAM mounts to telescope through the use of an adapter through the use of an adapter ‘boot’‘boot’

Controller mounts to boot but is Controller mounts to boot but is electrically isolated from telescopeelectrically isolated from telescope

Power Supplies and external Power Supplies and external controllers ride on cart next to controllers ride on cart next to telescope.telescope.

First Light Dec,17 2007First Light Dec,17 2007 Field of View = 13x13 arc-minutes, pixel scale = 0.76 “/pixField of View = 13x13 arc-minutes, pixel scale = 0.76 “/pix Optical Image of M42 Orion Star Forming Region from RBO (credit: Chris Rodgers). Optical Image of M42 Orion Star Forming Region from RBO (credit: Chris Rodgers).

BIRCAM Near-Infrared view of same region.BIRCAM Near-Infrared view of same region.

BIRCAM Performance at RBOBIRCAM Performance at RBO

Linear to 56,000 countsLinear to 56,000 counts Gain = 0.95 e- / ADUGain = 0.95 e- / ADU Read Noise = 18 e-Read Noise = 18 e-

Sky Brightness (Mag / arcsec²)Sky Brightness (Mag / arcsec²)

FilterFilter RBORBO KPNOKPNO CFHTCFHT

JJ 14.714.7 15.115.1 14.814.8

HH 14.414.4 13.113.1 13.413.4

KK 12.212.2 12.912.9 12.612.6

Science Opportunities with BIRCAM at Science Opportunities with BIRCAM at RBORBO

Sensitivity of BIRCAM is comparable to Sensitivity of BIRCAM is comparable to the 2 Micron All Sky Survey (2MASS). the 2 Micron All Sky Survey (2MASS).

BIRCAM allows for synoptic surveys of BIRCAM allows for synoptic surveys of relatively bright stars.relatively bright stars.Gamma Ray BurstsGamma Ray BurstsNearby SupernovaeNearby SupernovaeVariable Stars (esp. Cepheid Variables)Variable Stars (esp. Cepheid Variables)

Cepheid Variable StarsCepheid Variable Stars More massive more intrinsically luminous Cepheids have More massive more intrinsically luminous Cepheids have

longer periods. Plot intrinsic luminosity versus period to longer periods. Plot intrinsic luminosity versus period to obtain the PL relationobtain the PL relation

Mechanism for pulsation due to opacity (kappa-mechanism)Mechanism for pulsation due to opacity (kappa-mechanism) As star contracts the density and temperature riseAs star contracts the density and temperature rise The increase in temperature causes a shell of helium to ionizeThe increase in temperature causes a shell of helium to ionize Kramers law kappa = density * T^(-3.5), since temperature is Kramers law kappa = density * T^(-3.5), since temperature is

driving ionization, the density is the dominant term and the driving ionization, the density is the dominant term and the opacity increases. opacity increases.

Radiation is ‘trapped’ in high opacity conditions and the radiation Radiation is ‘trapped’ in high opacity conditions and the radiation pressure forces the star to expandpressure forces the star to expand

As the star expands, the density and temperature decrease. As the star expands, the density and temperature decrease. The Helium shell recombines with free electrons and the opacity The Helium shell recombines with free electrons and the opacity fallsfalls

Radiation ‘flows’ through low opacity conditions and radiation Radiation ‘flows’ through low opacity conditions and radiation pressure loses to gravity causing contraction.pressure loses to gravity causing contraction.

The Cepheid PL relationThe Cepheid PL relation The form of the PL relation is M = a Log(P) + bThe form of the PL relation is M = a Log(P) + b Infer the intrinsic luminosity by measuring the periodInfer the intrinsic luminosity by measuring the period Compare measured apparent brightness to inferred intrinsic luminosity to determine Compare measured apparent brightness to inferred intrinsic luminosity to determine

the distance. the distance. Measured apparent brightness effected by: extinction, line blanketing and binarity. Measured apparent brightness effected by: extinction, line blanketing and binarity. Observe in the NIR where these systematic effects are small compared to the optical. Observe in the NIR where these systematic effects are small compared to the optical.

Example from http://sci.esa.intExample from http://sci.esa.int

Cepheids and The Distance LadderCepheids and The Distance Ladder

Cepheids will link (via GAIA) Cepheids will link (via GAIA) trigonometric parallax to tertiary trigonometric parallax to tertiary distance indicators (they link distance indicators (they link relative distance measures to relative distance measures to absolute distance measure).absolute distance measure).

By observing in the NIR, By observing in the NIR, systematic effects are reduced.systematic effects are reduced.

Future distances to galaxies will Future distances to galaxies will be improved. be improved.

Measurements of the Hubble Measurements of the Hubble Constant will be better Constant will be better constrained. constrained.

See for example: Jacoby etal See for example: Jacoby etal (1992) (1992)

Cepheids observed in the NIRCepheids observed in the NIR

Samples Based on Samples Based on Cepheids that had known Cepheids that had known distances based on distances based on methods other than methods other than trigonometric parallaxtrigonometric parallax Laney & Stobie 1992Laney & Stobie 1992 Welch 1984Welch 1984 Barnes 1997Barnes 1997 A combined total of 59 A combined total of 59

quality Cepheidsquality Cepheids

BIRCAM survey BIRCAM survey BIRCAM will enable Northern Hemisphere survey of nearly 120 Cepheids in the J, H BIRCAM will enable Northern Hemisphere survey of nearly 120 Cepheids in the J, H

and K bands with periods between 4 and 40 days. and K bands with periods between 4 and 40 days. Well sampled light-curves produces standard NIR templatesWell sampled light-curves produces standard NIR templates The light-curves will provide for a future calibration of the NIR PL relation once GAIA The light-curves will provide for a future calibration of the NIR PL relation once GAIA

data is available. data is available. Detailed light-curves will enable a comparison to LMC Cepheids to identify systematic Detailed light-curves will enable a comparison to LMC Cepheids to identify systematic

differences (if any).differences (if any).

Data AnalysisData Analysis

Simple image reduction techniques Simple image reduction techniques (IRAF)(IRAF)

Standard star calibrationStandard star calibration NIR standards (Elias) and NIR standards (Elias) and

2MASS.2MASS. Cepheid photometryCepheid photometry

Differential aperture photometry of Differential aperture photometry of isolated Cepheids and secondary isolated Cepheids and secondary standardsstandards

Periods are knownPeriods are known Optimization of phase coverage Optimization of phase coverage

for each starfor each star Construct template light-curvesConstruct template light-curves

TimelineTimeline

Fall 2007 : Finish building camera and begin Fall 2007 : Finish building camera and begin observations at RBO (Complete). Write Instrument observations at RBO (Complete). Write Instrument paper for PASP.paper for PASP.

Spring / Summer 2008 : Continue observing at RBO Spring / Summer 2008 : Continue observing at RBO while reducing data and submit instrument paper. while reducing data and submit instrument paper. Finish observation and continue to reduce data and Finish observation and continue to reduce data and begin analysis. Write observations paper for AJ.begin analysis. Write observations paper for AJ.

Fall 2008 : Complete analysis of light-curves shapes Fall 2008 : Complete analysis of light-curves shapes including a comparison with the LMC sample. Start including a comparison with the LMC sample. Start writing results and thesis defense. Finish all tasks and writing results and thesis defense. Finish all tasks and defend thesis.defend thesis.