Spectral Characterization of
calibration lamps: STIS
An improved list of emission lines for
STIS Calibration Enhancement
Florian Kerber, ST-ECF
TIPS Meeting Sept 18th, 2003
2
Outline
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Calibration lamps for HST spectrographs
STIS Calibration Enhancement (STIS-CE)
ST-ECF Lamp Project
Laboratory Work
Results and Outlook
F. Kerber, ST-ECF
TIPS Sept 18th, 2003
3
Hollow cathode lamp
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Schematic drawing
F. Kerber, ST-ECF
TIPS Sept 18th, 2003
4
Pt/Ne hollow cathode lamp (IUE)
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Parameters of operation
– starting voltage: 300 V; operating voltage: 185 V; current:
10 - 60 mA, power consumption: 2 W @ 10 mA
– dimensions: 19.7 by 4.5 cm; weight: 71 (285) g
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Lifetime: > 750 h or 3 - 5 years of operation on IUE
 Source brightness stability: ~ 5 % after 5 - 10 min
 Rich emission line spectrum: 115 to 310 nm
 Wavelengths for 585 lines; Shenstone (1939)
F. Kerber, ST-ECF
TIPS Sept 18th, 2003
5
Hollow cathode lamps - HST (1990)
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Goddard High Resolution Spectrograph (GHRS):
115 - 320 nm; Pt-Ne ok
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Faint Object Spectrograph (FOS): 115 - 895 nm
– Addition of ~ 10% Cr to cathode extends coverage to 540
nm and Ne has lines up to 800 nm
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Space Telescope Imaging Spectrograph (STIS): 115
- 1000 nm
F. Kerber, ST-ECF
TIPS Sept 18th, 2003
6
Ready for Flight / Operations ?
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Engineering
– for both Pt-Ne and Pt/Cr-Ne thorough characterization of
lamps in terms of hardware performance
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Science Operations
– information on spectral output incomplete and crucial
wavelength information based on measurements done in
the 1930s (Pt) or absent (Cr)
– no spectral characterization of flight hardware
F. Kerber, ST-ECF
TIPS Sept 18th, 2003
7
HST Spectrograph Operations
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National Institute of Standards and Technology
– Pt-Ne lamp atlas 110 - 400 nm with ~ 3000 lines (Reader et
al., 1990, ApJS 72, 831)
F. Kerber, ST-ECF
TIPS Sept 18th, 2003
8
STIS Operations
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Pt line list from NIST
Cr lines can not be used because of lack of lab data
1st order long-slit modes have many Pt/Cr blends
– wavelengths assigned should be average weighted by line
intensity ratios, which are not known
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Empirical approach using 2-D polynomial fits
for Echelle modes
F. Kerber, ST-ECF
TIPS Sept 18th, 2003
9
STIS Calibration Enhancement
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Physical Model of STIS
– Spectrograph Model
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Laboratory Standards
– Good line list is required to realize full potential of
physical model
F. Kerber, ST-ECF
TIPS Sept 18th, 2003
10
ST-ECF Lamp Project
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Dedicated ESA funding
Measure spectrum of Pt/Cr-Ne lamp at NIST: 110 320 nm
Derive an accurate ( < 1/1000 nm) list of wavelengths
as input for STIS-CE
Quantify differences between Pt-Ne and Pt/Cr-Ne
spectrum
Look into aging effects of hollow cathode lamps
F. Kerber, ST-ECF
TIPS Sept 18th, 2003
11
Status of the ST-ECF Lamp Project
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First memorandum May 2001
Approved & funded in spring 2002
Contracts to NIST and IST (lamps) issued June 2002
FUV: 5 week measurement campaign Sep/Oct 2002
Intermediate results delivered Nov & Dec 2002
NUV: 6 week campaign in Apr/May 2003
Use within STIS-CE in progress
F. Kerber, ST-ECF
TIPS Sept 18th, 2003
12
NIST Eagle vacuum spectrograph
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10.7 m focal length, Vacuum UV (VUV) coverage
– 1.25 m/1 m diameter
– 13 m long, 15 m3
– 3 chambers
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Two 16 in. UV sensitive photographic plates
– 750 Å coverage
– 0.78 Å/mm resolution
F. Kerber, ST-ECF
TIPS Sept 18th, 2003
13
NIST Eagle vacuum spectrograph
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Synchrotron UV Facility (SURF III)
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Fourier Transform Spectrograph (FTS 700)
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Hollow cathode lamp
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ST-ECF Lamp Project - Status
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Measure spectrum of Pt/Cr-Ne lamp at NIST
– 10.7 m vacuum spectrograph: 113 - 183 nm
– FTS: 165 - 350 nm 
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Derive an accurate ( < 1/1000 nm) list of wavelengths
as input for STIS-CEs
– FUV: > 1100 lines total - 95% identified; 235 Cr
– NUV: > 3500 lines; ca 50% Cr in progress
F. Kerber, ST-ECF

TIPS Sept 18th, 2003
17
ST-ECF Lamp Project - Status
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Quantify differences between Pt-Ne and Pt/Cr-Ne
spectrum in progress
– addition of Cr changes of line ratios
– metal vs gas change as a function of operating current
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Aging of lamps
– accelerated aging test: 30s on/30s off cycle
1000 h without significant change
– vintage flight hardware
FOS & GHRS lamps
F. Kerber, ST-ECF
TIPS Sept 18th, 2003
18
Mystery feature “Clump” ~1430 Å
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Seen in both in FOS and STIS
F. Kerber, ST-ECF
TIPS Sept 18th, 2003
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Chromium “Clump” ~1430 Å
Cr-Ne
Pt/Cr-Ne
Pt-Ne
F. Kerber, ST-ECF
TIPS Sept 18th, 2003
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FUV Spectra: Pt vs Cr
Pt-Ne: old & new
F. Kerber, ST-ECF
New Cr
Faint Pt-Ne: old
TIPS Sept 18th, 2003
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NUV Spectra: Pt vs Cr
Pt/Cr-Ne
Cr-Ne
Pt-Ne
F. Kerber, ST-ECF
TIPS Sept 18th, 2003
22
Input for STIS-CE
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NUV c: 2843 Å
Lines seen : ~ 450
Pt: ~ 100 lines
Cr: ~ 700 lines
known
F. Kerber, ST-ECF
TIPS Sept 18th, 2003
23
Open Instrument Surgery
F. Kerber, ST-ECF
TIPS Sept 18th, 2003
24
Veteran Space Lamps
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After seven years
of operation in
space back to the
lab ...
FOS
GHRS
they still work
perfectly fine
F. Kerber, ST-ECF
TIPS Sept 18th, 2003
25
ST-ECF Lamp Project: Future
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NUV FTS data reduction, fall 2003
Return of FOS lamps to museum, Sept 23rd
Paper I, ApJS, Sept 2003 (FUV results)
STIS-CE new dispersion solutions, end 2003
Incorporate into calstis pipeline
STIS calibration proposal #10031 (PI: B. Mobasher)
F. Kerber, ST-ECF
TIPS Sept 18th, 2003
26
Lessons learned: Calibration ...
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requires attention to detail …
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requires expertise from different fields
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will give you better results
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is at the heart of scientific understanding
needs to be an integral part of any science project
F. Kerber, ST-ECF
TIPS Sept 18th, 2003
27
Lessons learned ...