TIPS/JIM
September 16, 2010
Agenda:
INS Division News (Jerry Kriss)
An Improved Treatment of the Linearity Correction of IR Detectors
(Massimo Robberto)
Monitoring the Wavelength Calibration Lamps for the Hubble Space
Telescope (Ilaria Pascucci)
The Non-Redundant Mask on JWST (Anand Sivaramakrishnan)
Next TIPS/JIM: October 21, 2010
Instruments Division News
09/16/2010
•
•
Welcome to
o Armin Rest, who joined the WIT team as an AURA Assistant Astronomer;
o Elena Mason, who joined the COS+STIS team as an ESA/AURA
Astronomer;
o Dean Hines, who joined the WIT team as an AURA Scientist;
o Anand Sivaramakrishnan, who returns to STScI as an AURA Scientist on
the WIT team;
o Kai Noeske, who joined the WFC3 team as an ESA/ESA Assistant
Astronomer;
o Jennifer Lotz, who joined the WIT team as an AURA Assistant
Astronomer.
Two more AURA astronomers and two more RIAs will be joining us over the next
couple of month!
•
HST news:
o HST had an SI C&DH upset last Thursday, the first in nearly a year. The
observatory was back to doing science with all instruments on line by
Saturday evening.
o Concerns about keeping the STIS and ACS MAMAs safe in the event of
another upset will lead to some flight software updates in the next few
months, and perhaps restrict some MAMA observation scheduling.
o The decline in FUV sensitivity of COS appears to have slowed to a rate of
5% per year, with the same rate at all wavelengths. The team is continuing
to monitor the sensitivity on a monthly basis.
•
JWST News:
o The JWST Test Assessment Team (which included Matt Mountain as a team
member and Erin Elliott as the Executive Secretary) issued its report to NASA
last week. It recommends several steps to simplify and shorten the ISIM and
observatory test plans. You can find the report on line at
http://www.jwst.nasa.gov/resources/JWST_TAT_Final_Report_100907.pdf.
We hope that Erin Elliott can give us a summary at next month’s TIPS/JIM.
o Upcoming workshop on IFUs in October!
•
Housing: We are close to signing a lease with JHU for space in the “Johns Hopkins at
Keswick” building (aka the Zurich Building) across the park in Hampden. This will
accommodate 40—50 people. A good guess is that it will be ready for occupancy in
~April 2011.
•
Our monthly INS Division lunch will be next Thursday, September 23, in the
boardroom.
•
Next TIPS/JIM is October 21, 2010.
TIPS/JIM
September 16, 2010
Agenda:
INS Division News (Jerry Kriss)
An Improved Treatment of the Linearity Correction of IR Detectors
(Massimo Robberto)
Monitoring the Wavelength Calibration Lamps for the Hubble Space
Telescope (Ilaria Pascucci)
The Non-Redundant Mask on JWST (Anand Sivaramakrishnan)
Next TIPS/JIM: October 21, 2010
An improved treatment of the linearity correc3on of IR detectors Massimo Robberto JWST/NIRCam STScI TIPS – Sep. 16, 2010 OUVERTURE IR detectors are non linear Linearity is assumed at the beginning of the ramp linear fit to the first 20 samples The “true” slope depends on the range of the assumed linear regime In fact, the angular coefficient of the true slope is hard to find… ACT 1 CURRENT STATUS How we do it now In the case of NICMOS and WFC3, we apply the following correc3on F are the measured counts Fc are the true counts. The calibra3on process assumes that they are known (fit to the first part of the ramp). Known both F’s, we derive the correc3on coefficients c2, c3 and c4 used for general linearity correc3on. Problems with this approach 1) We do not really know what is the real slope of the calibra3on frame, and our es3mate depends on the samples we use. 2) Physically, one has a linear true flux which is converted in a non‐linear measured count rate by the detector. This is not what we model! We modulate the observed data to get the real flux; instead, we should modulate the real flux to get the observed data. A controlled experiment using simulated data THIS IS THE WEIRD (NON POLYNOMIAL) NON‐LINEARITY TERM Let’s plot our baseline… … and derive the correc3on “a’la HST” I will assume that we know perfectly the true slope, i.e. problem 1 has been solved. I therefore get the best possible c coefficients. THIS IS THE POLYNOMIAL CORRECTION TERM The result is: Residuals ACT 2 A DIFFERENT APPROACH Let’s look at the equa3on Instead of (
2
Fc = F × 1 + c2 × F + c3 × F + c4 × F
3
)
We can try with the physically more correct expression: (
2
c
3
c
Fc × 1 + c2 × Fc + c3 × F + c4 × F
i.e. we modulate the real flux Fc to get F, not viceversa )= F
Method In Equa3on (
2
c
3
c
Fc × 1 + c2 × Fc + c3 × F + c4 × F
)= F
the Fc and c2,c3,c4 values are unknown. I use IDL/curvefit.pro to derive them from the set of known ti and measured Fi: having defined the func3on: 0.3% error on the slope! Linearity correc3on From the values of c2, c3, an c3 one can derive Fc by solving the equa3on: Fc =
F
(
1 + c2 × Fc + c3 × Fc2 + c4 × Fc3
Need to use an itera3ve method: )
Results i=0 1 2 4 Check: different flux rate Same “detector”, i.e. exponen3al non‐linearity term Correc3on: old vs. new method Old New Conclusion The current strategy we implement to correct for non‐linearity seems less than ideal. 1)  Problems with the es3mate of the coefficients, which depend on the assumed “linearity” region of the detector 2)  Problems with the equa3on, which does not correctly describes the non‐linearity effect The new method has two advantages 1)  Coefficients are es3mated without any assump3on on the true, linear flux 2)  The correct equa3on, with an itera3ve solve, seems to provide a much beher es3mate of the true linear flux. Check on real data is in progress TIPS/JIM
September 16, 2010
Agenda:
INS Division News (Jerry Kriss)
An Improved Treatment of the Linearity Correction of IR Detectors
(Massimo Robberto)
Monitoring the Wavelength Calibration Lamps for the Hubble Space
Telescope (Ilaria Pascucci)
The Non-Redundant Mask on JWST (Anand Sivaramakrishnan)
Next TIPS/JIM: October 21, 2010
Monitoring of the Wavelength Calibration Lamps
for the Hubble Space Telescope
ILARIA PASCUCCI
Space Telescope Science Institute
Department of Physics & Astronomy, Johns Hopkins University
Pascucci, I. , Proffitt, C., Ghavamian, P., Sahnow, D., Oliveira, C., Aloisi,
A., Keyes, T., Penton, S. V. – Proc. SPIE, Vol. 7731, 77313B (2010)
STIS and COS Lamps
STIS : 3 hollow cathode Pt-Cr-Ne lamps
~1130-3200Å
~5400-8000Å
~3200-5400Å
COS : 2 hollow cathode Pt-Ne lamps
When do we take a lamp spectrum?
STIS : every time we use a new grating or tilt position and generally after ~1 orbit
COS : lamp exposure contemporaneous to science observations
Causes for lamps fading
typical lifetime 15,000 mA h or 1,500 h at 10 mA current
1. Metals sputtered from the cathode trap Ne atoms
➔ reduced gas pressure ➔ need higher turn-on voltage
2. Aging of the barium getter ➔ impurities mainly H ➔ H lines
3. COS: lamp beams become larger with time (not intrinsic fading)
Increase lamp voltage with use
Nave et al. 2008
STIS Lamps
STIS : 3 Pt-Cr-Ne lamps
–
LINE, HITM1 and HITM2
Different locations and optics: LINE brightest on the detector ➔ FUV echelle modes
HITM1 and 2 ➔ optical low-res modes
STIS – Lamps Fading with Time STIS – Lamps Fading in the FUV
STIS – Lamp flux vs Usage
STIS – Current Lamp Flux Ratios
PID 12079 : 4 internal orbits
STIS – Early vs Recent Lamp Exposures
STIS – The Most Affected Setting
current exp time with LINE = 46s
➔ allow for the HITM2 lamp
COS and STIS Lamp comparison
when the COS sensitivity degradation is removed
Aged-lamps Intensities
Nave et al. 2008
Summary
•  The STIS LINE lamp, which was the brightest at the beginning of operation in 1997,
has faded dramatically at the shortest FUV wavelengths (1150-1200Å) and is now
fainter than the other two STIS lamps
•
The STIS LINE lamp output remains higher than the HITM1 and HITM2 lamp
outputs by factors of ~5-10 at all wavelengths > 1300Å
•  The
fading of the STIS LINE lamp between 1997 and 2010 in absolute terms is
factor of ~15 at the very short FUV wavelengths, much greater than what expected
from accelerated aging tests in the laboratory
•
We have evidence that all STIS lamps fade even when they are not used indicating
that on-orbit factors are impacting the lifetime of the lamps
•  The
6-month monitoring of the COS P1 lamp shows that the lamp output fades
similarly to the STIS lamps as a function of lamp usage
Pascucci, I. , Proffitt, C., Ghavamian, P., Sahnow, D., Oliveira, C., Aloisi,
A., Keyes, T., Penton, S. V. – Proc. SPIE, Vol. 7731, 77313B (2010)
TIPS/JIM
September 16, 2010
Agenda:
INS Division News (Jerry Kriss)
An Improved Treatment of the Linearity Correction of IR Detectors
(Massimo Robberto)
Monitoring the Wavelength Calibration Lamps for the Hubble Space
Telescope (Ilaria Pascucci)
The Non-Redundant Mask on JWST (Anand Sivaramakrishnan)
Next TIPS/JIM: October 21, 2010
non-redundant masking on JWST TFI
Anand Sivaramakrishnan
STScI
JWST TFI Science Team (NRM lead)
Stony Brook Physics & Astronomy
JAM team lead (JWST Aperture masking, GPI, P1640)
1 JAM Team
JWST Aperture Masking team
Anand Sivaramakrishnan (Lead) Peter Tuthill, Mike Ireland (U Sydney) James Lloyd (Cornell) Frantz MarCnache (Subaru) Rene Doyon (TFI) David Lafreniere (TFI) Remi Soummer (JWST WFS&C) Chas Beichman (NIRCam) Barry McKernan, Saavik Ford (AGNs, QSOs GBHCs)
Marshall Perrin (STScI - IFU on GPI)
Laurent Pueyo (NRM on GPI, Sagan Felolw)
Michael McElwain (IFU on Keck, NSF Fellow)
Sasha Hinkley (IFU, Palomar Hale, Sagan Fellow)
2 High contrast is difficult
from the ground
Racine 1999
Fitzgerald
& Graham 2006 10ms 2um
Fitzgerald & Graham 2006
Racine et al. PASP 1999 Sivaramakrishnan et al ApJL 2002, Perrin et al. ApJ 2003, Aime & Soummer ApJ 2004, Fitzgerald & Graham 2006, Soummer et al. 2007,... 3 Optimal data analysis
Fitzgerald & Graham 2006 10ms 2um
Bayesian approach to combining all data Marois et al. 2008 Science “ADI” Lafreniere et al 2007 refined methods ‐ LOCI 4 WR 104 Discovery Images
NRM on Keck – model fitting
HI RES FROM GROUND
Apr 1998 Jun 1998 Sep 1998 Tuthill et al, Nature 1999 50 mas (75 AU)
5 HIGH ANGULAR RESOLUTION IS DIFFICULT FROM SPACE
Roll subtracCon 3 Mjup 12” separaCon Kalas et al. Science 2008 6 NRM cf. Conventional AO (ground)
7 Signal is not the problem
Throw away light but get the science!
Rayleigh Criterion δθ = 1.22 λ/D Michelson Criterion δθ = 0.5 λ/D 8 JWST TFI NRM
Taurus proto‐
planets 9 10 Fourier Components
Fourier Components
FGS-TFI g7s6 mask
50mm OD mask, 39mm OD pupil, SS
part
Simulated PSF PSF’s power spectrum g7s6sc Blocking off 11 of 18 PM segments leads to otherwise inaccessible science with JWST 13 Closure Phase
Stable JWST closure amplitudes yield true imaging, not just model‐fi@ng
14 9 hole mask
•  36 baselines
Closure Phase
•  84 closure triangles
(28 independent)
φ(2-1) = φ0(2-1)
φ(1-3) = φ0(1-3)
φ(3-2) = φ0(3-2)
measured
phase
=
+
+
+
φ2-φ1
φ1-φ3
φ3-φ2
Signal extracCon cf PSF suppression 15 intrinsic
+
instrumental
TFI G7S6 mask
50mm OD mask TFI-PM pupil mapping, titanium
part
Semi-major
axis (AU))
Predicted JWST FGS-TFI survey
part
0.4
0.5
0.5
0
DETECTION PROBABILITIES
0.5
0.2
0.5
0.6
Companion mass <=10 MJ
1 hour exposure
10 mag contrast floor
4.4 micron
0.7
0.1
0.6
0.8
0.3
JWST coronagraph &
ExAOC survey simulations:
Beichman, Krist, Trauger,
Greene, Oppenheimer,
Sivaramakrishnan, Doyon,
Bocaletti, Barman, Rieke
PASP 2010
0.7
17 0.1
Log10(M/MJ)
Predicted JWST FGS-TFI survey
results
JWST coronagraph & ExAOC survey simulations: Beichman, Krist, Trauger, Greene, Oppenheimer,
Sivaramakrishnan, Doyon, Bocaletti, Barman, Rieke PASP 2010
18 Undergrad NRM at Stony Brook
ParmenCer & Sivaramakrishnan Inexpensive CCD camera, lens, laser-cut SS mask
SB NRM Testbed Mark II – mirror instead of lens
2010 NSF REU Alexandra Greenbaum to make a ‘star+planet’ for the testbed
Undergrad NRM data – space-like
ParmenCer & Sivaramakrishnan FT of ‘interferogram’: absolute value and phase
GOAL: Develop estimates of contrast of faint point source companions that JWST can achieve
in IR to see protoplanets in Taurus, and other places planets are being formed. Stable images,
data reduction algorithm development, help plan JWST science & observing proposals
Future extragalactic space-based observations of disks and dusty tori around massive black
holes at centers of external galaxies – JWST (& ATLAST)
Undergrad NRM data – space-like
ParmenCer & Sivaramakrishnan Palomar IFU NRM data
Sivaramakrishnan Zimmerman Tuthill Lloyd Ireland Oppenheimer Soummer Simon Calibrator
First IFU NRM data P1640 J+H IFU on Palomar Target
ISSUES for JWST FGS‐TFI NRM Dither for CRs & bad pixels) More study
Bright stars possible (M >= 2 ) Good target acquisiLon cures calibraLon troubles Intrapixel sensiLvity, persistence, flat field accuracy studies under part waySsimulated L2 CR library (Robberto), full data reducLon pipeline g7s6sc Robust to PM actuator freezing Mask is also a wavefront sensor Robust backup for coarse phasing QUESTIONS: How good can the contrast really get,??? Develop credible science for Wyoming 2011 23 Simulated PSF