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Hubble Space Telescope
WFPC2 STAN

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| WFPC2
| STScI Analysis Newsletter
| WFPC2 STAN 53
| November 2002
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CONTENTS:

- WFPC2 Close-Out Calibration Programs

- Pointing Uncertainties

- Instrument Science Reports Since The Previous STAN: 
     02-04 An Analysis of WFPC2 Filter Positional Anomalies           
     02-05 WFPC2 Cycle 11 Calibration Plan
     02-06 SMOV3b
     02-07 Updated Contamination Rates for WFPC2 UV Filters

- Jay Anderson and Ivan King Astrometry Paper on the Website

- Re-organization of the WFPC2 Documents on the Website

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WFPC2 Close-Out Calibration Programs

-Anton Koekemoer

Cycle 12 is currently planned to be the last full cycle for 
WFPC2, which will be de-orbited during the next Servicing 
Mission (SM4) when it is scheduled to be replaced with WFC3. 
Therefore, we are currently soliciting input from the 
community as to whether there are any additional calibration 
programs that should be carried out with WFPC2 before it is 
de-orbited, in order to improve or augment calibration 
accuracies or explore new types of calibration. In conjunction 
with the recent HST Calibration Workshop, a special splinter 
session was devoted to the topic of WFPC2 close-out, and a 
number of possible programs were identified. Some examples of 
these included further refinements to the geometric solution, 
improvements to the filter photometric characterizations, 
better measurements of the PSF wings on large scales, and 
improving the CTE characterization.

We therefore encourage any interested members of the community 
to contact us with suggestions for Cycle 12 calibration 
observations, which we will be defining in the next few months. 
These may fall under the above categories or alternatively 
address other issues that may be required in order to improve 
the scientific value of archival WFPC2 data. We also remind 
observers of the opportunity to submit Calibration Outsourcing 
proposals of your own in Cycle 12. These may be observational, 
archival, or both. Additional topics for Calibration 
Outsourcing programs are listed at this website:
http://www.stsci.edu/instruments/wfpc2/wfpc2_out.html

Consultation with the WFPC2 group at STScI is also welcomed on 
any of these topics (just send an email to "help@stsci.edu" 
addressing the topic of WFPC2 Close-Out Calibration Programs). 
We will be happy to provide advice and collaborative input, 
and we strongly encourage members of the community to take the 
initiative in proposing any close-out programs that you feel 
would enhance the quality of some particular aspect of WFPC2 
science.

Pointing Uncertainties

-Gabriel Brammer

An offset of 1-2 arcsec is found between the predicted and 
actual pointing positions of a set of observations of the 
standard star GRW+70D5824 taken between Jan 1999 and Aug 
2002. The direction of the offset in chip coordinates 
changes throughout the course of the year as the telescope 
orientation changes, causing the overall uncertainty in the 
absolute pointing of WFPC2 to be somewhat higher than the ~1 
arcsec uncertainty in guide star positions. The r.m.s. of 
the pointings is approximately 1.5 arcsec, but two individual 
pointings of the same target observed about 6 months apart 
could differ by as much as 5 arcsec in the worst cases. This 
scatter is primarily due to misalignments of the three Fine 
Guidance Sensors, and is expected to be improved by an update 
to the observatory aperture file implemented on 20 Oct, 2002. 
Users requiring high absolute astrometric precision for a 
given image should measure positions relative to an 
astrometric standard found on the same frame, if possible. 
For more information, see the paper by Brammer, Whitmore, 
and Koekemoer in the proceedings of the 2002 HST Calibration 
Workshop (to be published in 2003).

An Analysis of WFPC2 Filter Positional Anomalies

-Shireen Gonzaga, Sylvia Baggett, John Biretta

In March of 2001, a routine analysis of FR533N VISFLAT images 
revealed an anomaly: the filter wheel appeared to be offset 
by about 0.42 degrees in some images. This offset angle is 
close to 0.5 degrees, which corresponds to one "filter step," 
(i.e., one increment in movement of the filter wheel by the 
filter electronics). These offsets are not a recent phenomena, 
and have been found in data as far back as mid-1994. This 
document describes a more exhaustive analysis of the filter 
wheel rotation anomaly: flatfield images for all available 
filters in the archive were inspected to determine if they 
exhibited similar behavior. Only filters that projected 
unique features (such as pinholes) onto the image were 
useful because these features were needed to detect the 
offsets. In addition to the previously-reported problem 
with FR533N, filter wheel rotation offsets have also now 
been found in these additional filter configurations: F375N, 
FR418N, FR533N18, FR533N33, FR533P15, FR680N, FR680N33, 
FQCH4N, FQCH4N15, and FQCH4P15. The offset angle was found 
to be 0.42 +/- 0.06. The occurrence rate of the offset error 
ranges from 0% to 40% for these filters (based on samples of 
20 images or larger). It is also apparent that some filters 
(e.g. F160BW) show no rotation errors. In general, the 
errors will have little impact on GO science, though 
photometric errors can reach a few percent in worst-case 
scenarios. There is also some hint that the problem may be 
getting worse with time. Currently, the cause of the anomaly 
is not completely understood. Cycle 10 and cycle 11 calibration
programs will continue monitoring these filter wheel offsets.

WFPC2 Cycle 11 Calibration Plan

-S. Gonzaga, and the WFPC2 Group

The Cycle 11 Calibration Program, extending from July 1, 2002 
to June 30, 2003 will continue to monitor the health of WFPC2, 
using the standard suite of calibrations, as well as some 
special programs to characterize other aspects of the 
instrument. The most significant change in the routine 
monitors concerns the length of time between decontaminations. 
This period has been increased from 28 days to 49 days because 
data from the last few cycles indicate that the contamination 
rate has been decreasing. Special programs include more efforts 
to characterize CTE, a revisit of the long-vs.-short anomaly,
photometry of non-standard filters for creating new zeropoints, 
as well as a program to cross-calibrate WFPC2 and ACS filters. 
Because there are significantly fewer primary WFPC2 science 
observations in cycle 11, with the advent of ACS, the 
calibration plan has been significantly scaled back, but 
without sacrificing the quality of data required to calibrate 
the instrument. For cycle 11, 40 external orbits will be used, 
compared to 61 in cycle 10.

WFPC2 SMOV3b

-Anton Koekemoer

Servicing Mission 3B (SM3B) took place in March 2002, and the 
Wide Field and Planetary Camera 2 (WFPC2) resumed operations 
on March 23, 2002, after having been placed in an inactive 
mode during the Servicing Mission. We describe here the results 
from an extensive series of tests and observations that we 
carried out with WFPC2 as part of the subsequent Observatory 
Verification phase. These tests included UV monitoring of 
possible contamination, performance checks of the biases, 
darks and other internal calibrations, as well as PSF 
measurements and flatfield verification. The results from these
tests show that there are no significant changes in the 
operational behavior of the camera with respect to its pre-SM3B
performance.

Updated Contamination Rates for WFPC2 UV Filters

-Matt McMaster and Brad Whitmore

Photometric monitoring observations of a white dwarf standard 
(GRW+70D5824) have been used to update the contamination rates 
for WFPC2 UV filters. Observations from April 1994 through May 
2002 were used in the analysis. In general, the contamination 
rates have declined by roughly 50% for most of the filters 
during this period. Least-squares fits have been made to the 
data to allow observers to remove the effects of contamination 
in their WFPC2 observations.

An Improved Distortion Solution for HST's WFPC2

-Jay Anderson and Ivan King

A preprint of a new paper by Jay Anderson and Ivan King on 
an improved distortion solution for WFPC2 is available on 
the WFPC2 website. The paper should appear in the Jan 2003 
version of the PASP. A separate link points to a Fortran 
routine that implements the distortion solution.

Re-organization of the WFPC2 Documents on the Website

-Inge Heyer

The documents section on the WFPC2 website has been
re-organized to make documents easier to find. The documents
have been grouped into Documents (Instrument Handbook, 
manuals, etc.) and General Resources (reference file lists, 
memos, etc.). Each section has an overview, and in addition, 
we have created a one-page sheet to list the primary 
references needed for proposal preparation and data 
reduction. Community feedback on this re-organization is 
welcomed.

+----------------------------------------------------------+
| Recent WFPC2-related Papers/Preprints
+----------------------------------------------------------+

We draw your attention to these papers, based on WF/PC and 
WFPC2 data, that have appeared since the last STAN, or will 
appear in the next few months. This list includes all 
preprints received by the STScI Library not yet published 
in the journals. Please remember to include our Library in 
your preprint distribution list.

AFANASIEV, V.; SIL'CHENKO, O.K. "Complex Formation History 
of the Lenticular Galaxies with Stellar Counterrotation: 
NGC 4128 and NGC 4550" AJ 124: 706-721, 2002

AGUERRI, J.A.L.; TRUJILLO, I. "Restrictions to the Galaxy 
Evolutionary Models from the Hawaiian Deep Fields SSA13 and 
SSA22" MNRAS 333: 633-651, 2002

ALVES, D.R.; REJKUBA, M.; MINNITI, D.; COOK, K.H. "K-band 
Red Clump Distance to the Large Magellanic Cloud" ApJ 573: 
L51-L54, 2002

BALOGH, M.L.; COUCH, W.J.; SMAIL, I.; BOWER, R.G.; GLAZEBROOK, 
K. "An H alpha Survey of the Rich Cluster A 1689" MNRAS 335: 
10-22, 2002

BENNERT, N.; FALCKE, H.; SCHULZ, H.; WILSON, A.S.; WILLS, 
B.J. "Size and Structure of the Narrow-Line Region of Quasars" 
ApJ 574: L105-L109, 2002

BENSON, A.J.; ELLIS, R.S.; MENANTEAU, F. "On the Continuous 
Formation of Field Spheroidal Galaxies in Hierarchical Models 
of Structure Formation" MNRAS 336: 564-576, 2002

BESWICK, R.J.; PEDLAR, A.; MCDONALD, A.R. "Sub-arcsecond 
Atomic Hydrogen Absorption in the Seyfert Galaxies NGC 7674 
and NGC 7469" MNRAS 335: 1091-1099, 2002

BROTHERTON, M.S.; GRABELSKY, M.; CANALIZO, G.; VAN BREUGEL, 
W.; FILIPPENKO, A.V.; CROOM, S.; BOYLE, B.; SHANKS, T. "Hubble 
Space Telescope Imaging of the Poststarburst Quasar UNJ1025-0040: 
Evidence for Recent Star Formation" PASP 114: 593-601, 2002

BUJARRABAL, V.; ALCOLEA, J.; SANCHEZ CONTRERAS, C.; SAHAI, R. 
"HST Observations of the Protoplanetary Nebula OH 231.8+4.2: 
the Structure of the Jets and Shocks" A&A 389: 271-285, 2002

CHATTERJEE, S.; CORDES, J.M. "Bow Shocks from Neutron Stars: 
Scaling Laws and Hubble Space Telescope Observations of the 
Guitar Nebula" ApJ 575: 407-418, 2002

CORBIN, M.R.; O'NEIL, E.; RIEKE, M.J. "Hubble Space Telescope 
NICMOS Imaging of the Core of M87" AJ 124: 183-190, 2002

COURBIN, F.; MEYLAN, G.; KNEIB, J.-P.; LIDMAN, C. "Cosmic 
Alignment Towards the Radio Einstein Ring PKS 1830-211?" 
ApJ 575: 95-102, 2002

CROCKER, M.M.; DAVIS, R.J.; SPENCER, R.E.; EYRES, S.P.S.; 
BODE, M.F.; SKOPAL, A. "The Symbiotic Star CH Cygni -- 
III. A Precessing Radio Jet" MNRAS 335: 1100-1108, 2002

CUZZI, J.N.; FRENCH, R.G.; DONES, L. "HST Multicolor (255-1042 
nm) Photometry of Saturn's Main Rings. I: Radial Profiles, 
Phase and Opening Angle Variations, and Regional Spectra" 
Icarus 158: 199-223, 2002

DA COSTA, G.S.; ARMANDROFF, T.E.; CALDWELL, N. "The Dwarf 
Spheroidal Companions to M31: WFPC2 Observations of Andromeda 
III" AJ 124: 332-348, 2002

DOI, T.; O'DELL, C.R.; HARTIGAN, P. "Internal Velocities in 
the Orion Nebula: Large Proper-Motion Features" AJ 124: 
445-463, 2002

DROZDOVSKY, I.O.; SCHULTE-LADBECK, R.E.; HOPP, U.; GREGGIO, 
L.; CRONE, M.M. "The Dwarf Irregular/Wolf-Rayet Galaxy NGC 
4214. I. A New Distance, Stellar Content, and Global 
Parameters" AJ 124: 811-827, 2002

ERWIN, P.; SPARKE, L.S. "Double Bars, Inner Disks, and Nuclear 
Rings in Early-Type Disk Galaxies" AJ 124: 65-77, 2002

EYRES, S.P.S.; BODE, M.F.; SKOPAL, A.; CROCKER, M.M.; DAVIS, 
R.J.; TAYLOR, A.R.; TEODORANI, M.; ERRICO, L.; VITTONE, A.A.; 
ELKIN, V.G. "The Symbiotic Star CH Cygni -- II. The Ejecta 
from the 1998-2000 Active Phase" MNRAS 335: 526-538, 2002

FARRAH, D.; MEIKLE, W.P.S.; CLEMENTS, D.; ROWAN-ROBINSON, M.; 
MATTILA, S. "The Host Galaxies of Type Ia Supernovae at z = 
0.6" MNRAS 336: L17-L21, 2002

GIRARDI, L.; BERTELLI, G.; BRESSAN, A.; CHIOSI, C.; GROENEWEGEN, 
M.A.T.; MARIGO, P.; SALASNICH, B.; WEISS, A. "Theoretical 
Isochrones in Several Photometric Systems. 
I. Johnson-Cousins-Glass, HST/WFPC2, HST/NICMOS, Washington, 
and ESO Imaging Survey Filter Sets" A&A 391: 195-212, 2002

GOAD, M.R.; ROBERTS, T.P.; KNIGGE, C.; LIRA, P. "The Optical 
Counterpart of the Ultraluminous X-ray Source NGC 5204 X-1" 
MNRAS 335: L67-L70, 2002

GONZALEZ DELGADO, R.M.; ARRIBAS, S.; PEREZ, E.; HECKMAN, T. 
"Is a Minor Merger Driving the Nuclear Activity in the Seyfert 
2 Galaxy NGC 2110?" ApJ 579: 188-204, 2002

HALL, P.B.; RICHARDS, G.T.; YORK, D.G.; KEETON, C.R.; BOWEN, 
D.V.; SCHNEIDER, D.P.; SCHLEGEL, D.J.; BRINKMANN, J. "The 
Redshift of a Lensing Galaxy in PMN J0134-0931" ApJ 575: 
L51-L54, 2002

HAMILTON, T.S.; CASERTANO, S.; TURNSHEK, D.A. "The Luminosity 
Function of QSO Host Galaxies" ApJ 576: 61-74, 2002

HANSEN, B.M.S.; BREWER, J.; FAHLMAN, G.G.; GIBSON, B.K.; 
IBATA, R.; LIMONGI, M.; RICH, R.M.; RICHER, H.B.; SHARA, M.M.; 
STETSON, P.B. "The White Dwarf Cooling Sequence of the 
Globular Cluster Messier 4" ApJ 574: L155-L158, 2002

HARRIS, W.E.; HARRIS, G.L.H.; HOLLAND, S.T.; MCLAUGHLIN, 
D.E. "Structural Parameters for Globular Clusters in NGC 5128" 
AJ 124: 1435-1451, 2002

HESTER, J.J.; MORI, K.; BURROWS, D.; GALLAGHER, J.S.; GRAHAM, 
J.R.; HALVERSON, M.; KADER, A.; MICHEL, F.C.; SCOWEN, P. 
"Hubble Space Telescope and Chandra Monitoring of the Crab 
Synchrotron Nebula" ApJ 577: L49-L52, 2002

HOEKSTRA, H.; FRANX, M.; KUIJKEN, K.; VAN DOKKUM, P.G. "HST 
Large-Field Weak Lensing Analysis of MS 2053-04: Study of the 
Mass Distribution and Mass-to-Light Ratio of X-ray Luminous
Clusters at 0.22 < z < 0.83" MNRAS 333: 911-922, 2002

HOMEIER, N.; GALLAGHER, J.S. III; PASQUALI, A. "The Star Cluster 
System of the NGC 7673 Starburst" A&A 391: 857-873, 2002

HUGGINS, P.J.; MAURON, N. "Small Scale Structure in 
Circumstellar Envelopes and the Origin of Globules in 
Planetary Nebulae" A&A 393: 273-283, 2002

JORDAN, A.; COTE, P.; WEST, M.J.; MARZKE, R.O. "The Relative 
Ages of the Globular Cluster Subpopulations in M87" ApJ 576: 
L113-L116, 2002

KARACHENTSEV, I.D.; SHARINA, M.E.; MAKAROV, D.I.; DOLPHIN, 
A.E.; GREBEL, E.K.; GEISLER, D.; GUHATHAKURTA, P.; HODGE, P.W.; 
KARACHENTSEVA, V.E.; SARAJEDINI, A.; SEITZER, P.
"The Very Local Hubble Flow" A&A 389: 812-824, 2002

KERBER, L.O.; SANTIAGO, B.X.; CASTRO, R.; VALLS-GABAUD, D. 
"Analysis of Colour-Magnitude Diagrams of Rich LMC Clusters: 
NGC 1831" A&A 390: 121-132, 2002

KUIJKEN, K.; RICH, R.M. "Hubble Space Telescope WFPC2 Proper 
Motions in Two Bulge Fields: Kinematics and Stellar 
Population of the Galactic Bulge" AJ 124: 2054-2066, 2002

KUNDU, A.; MACCARONE, T.J.; ZEPF, S.E. "The Low-Mass X-ray 
Binary-Globular Cluster Connection in NGC 4472" ApJ 574: 
L5-L9, 2002

LARSEN, S.S. "The Luminosity Function of Star Clusters in 
Spiral Galaxies" AJ 124: 1393-1409, 2002

LARSEN, S.S.; BRODIE, J.P.; SARAJEDINI, A.; HUCHRA, J.P. 
"Structural Parameters and Dynamical Masses for Globular 
Clusters in M33" AJ 124: 2615-2624, 2002

LAUER, T.R.; GEBHARDT, K.; RICHSTONE, D.; TREMAINE, S.; 
BENDER, R.; BOWER, G.; DRESSLER, A.; FABER, S.M.; FILIPPENKO, 
A.V.; GREEN, R.; GRILLMAIR, C.J.; HO, L.C.; KORMENDY, J.; 
MAGORRIAN, J.; PINKNEY, J.; LAINE, S.; POSTMAN, M.; VAN DER 
MAREL, R.P. "Galaxies with a Central Minimum in Stellar 
Luminosity Density" AJ 124: 1975-1987, 2002

LI CAUSI, G.; DE MARCHI, G.; PARESCE, F. "On the Accuracy of 
the Signal-to-Noise Estimates Obtained with the Exposure-Time 
Calculator of the Wide Field Planetary Camera 2 on Board the 
Hubble Space Telescope" PASP 114: 770-779, 2002

LIRA, P.; WARD, M.J.; ZEZAS, A.; MURRAY, S.S. "Chandra HRC 
and HST Observations of NGC 6240: Resolving the Active Galactic 
Nucleus and Starburst" MNRAS 333: 709-714, 2002

LUBIN, L.M.; OKE, J.B.; POSTMAN, M. "Evidence for Cluster 
Evolution from an Improved Measurement of the Velocity 
Dispersion and Morphological Fraction of Cluster 1324+3011 
at z = 0.76" AJ 124: 1905-1917, 2002

MENDEZ, B.; DAVIS, M.; MOUSTAKAS, J.; NEWMAN, J.; MADORE, 
B.F.; FREEDMAN, W.L. "Deviations from the Local Hubble Flow. 
I. The Tip of the Red Giant Branch as a Distance Indicator" 
AJ 124: 213-233, 2002

MOFFAT, A.F.J.; CORCORAN, M.F.; STEVENS, I.R.; SKALKOWSKI, 
G.; MARCHENKO, S.V.; MUCKE, A.; PTAK, A.; KORIBALSKI, B.S.; 
BRENNEMAN, L.; MUSHOTZKY, R.; PITTARD, J.M.; POLLOCK, A.M.T.; 
BRANDNER, W. "Galactic Starburst NGC 3603 from X-rays to 
Radio" ApJ 573: 191-198, 2002

NELSON, C.A.; COOK, K.H.; AXELROD, T.S.; MOULD, J.R.; ALCOCK, 
C. "A Proper-Motion Survey for White Dwarfs with the Wide 
Field Planetary Camera 2" ApJ 573: 644-661, 2002

PALMA, C.; ZONAK, S.G.; HUNSBERGER, S.D.; CHARLTON, J.C.; 
GALLAGHER, S.C.; DURRELL, P.R.; ENGLISH, J. "The Beginning 
of the End: Hubble Space Telescope Images of Seyfert's Sextet" 
AJ 124: 2425-2439, 2002

PAPADEROS, P.; IZOTOV, Y.I.; THUAN, T.X.; NOESKE, K.G.; 
FRICKE, K.J.; GUSEVA, N.G.; GREEN, R.F. "The Blue Compact 
Dwarf Galaxy I Zw 18: a Comparative Study of Its 
Low-Surface-Brightness Component" A&A 393: 461-483, 2002

PASQUALI, A.; NOTA, A.; SMITH, L.J.; AKIYAMA, S.; MESSINEO, 
M.; CLAMPIN, M. "Multiwavength Study of the Nebula Associated 
with the Galactic LBV Candidate HD 168625" AJ 124: 1625-1635, 
2002

PENG, C.Y. "Assessing Formation Scenarios for the Double 
Nucleus of M31 Using Two-Dimensional Image Decomposition" 
AJ 124: 294-309, 2002

PERLMAN, E.S.; STOCKE, J.T.; CARILLI, C.L.; SUGIHO, M.; 
TASHIRO, M.; MADEJSKI, G.; WANG, Q.D.; CONWAY, J. "The 
Apparent Host Galaxy of PKS 1413+135: Hubble Space Telescope, 
ASCA and Very Long Baseline Array Observations" 
AJ 124: 2401-2412, 2002

PIOTTO, G.; KING, I.R.; DJORGOVSKI, S.G.; SOSIN, C.; ZOCCALI, 
M.; SAVIANE, I.; DE ANGELI, F.; RIELLO, M.; RECIO BLANCO, A.; 
RICH, R.M.; MEYLAN, G.; RENZINI, A. "HST Color-Magnitude
Diagrams of 74 Galactic Globular Clusters in the HST F439W 
and F555W Bands" A&A 391: 945-965, 2002

PIZZELLA, A.; CORSINI, E.M.; MORELLI, L.; SARZI, M.; SCARLATA, 
C.; STIAVELLI, M.; BERTOLA, F. "Nuclear Stellar Disks in Spiral 
Galaxies" ApJ 573: 131-137, 2002

POULET, F.; CUZZI, J.N.; FRENCH, R.G.; DONES, L. "A Study of 
Saturn's Ring Phase Curves from HST Observations" Icarus 158: 
224-248, 2002

PRITZL, B.J.; ARMANDROFF, T.E.; JACOBY, G.H.; DA COSTA, G.S. 
"The Dwarf Spheroidal Companions to M31: Variable Stars in 
Andromeda VI" AJ 124: 1464-1485, 2002

PUZIA, T.H.; ZEPF, S.E.; KISSLER-PATIG, M.; HILKER, M.; 
MINNITI, D.; GOUDFROOIJ, P. "Extragalactic Globular Clusters 
in the Near-Infrared. II. The Globular Clusters Systems of 
NGC 3115 and NGC 4365" A&A 391: 453-470, 2002

RAGES, K.; HAMMEL, H.B.; LOCKWOOD, G.W. "A Prominent 
Apparition of Neptune's South Polar Feature" Icarus 159: 
262-265, 2002

RICHER, H.B.; BREWER, J.; FAHLMAN, G.G.; GIBSON, B.K.; HANSEN, 
B.M.; IBATA, R.; KALIRAI, J.S.; LIMONGI, M.; RICH, R.M.; 
SAVIANE, I.; SHARA, M.M.; STETSON, P.B. "The Lower Main 
Sequence and Mass Function of the Globular Cluster Messier 4" 
ApJ 574: L151-L154, 2002

RUBIN, R.H.; BHATT, N.J.; DUFOUR, R.J.; BUCKALEW, B.A.; 
BARLOW, M.J.; LIU, X.-W.; STOREY, P.J.; BALICK, B.; FERLAND, 
G.J.; HARRINGTON, J.P.; MARTIN, P.G. "Temperature Variations 
from Hubble Space Telescope Imagery and Spectroscopy of NGC 
7009" MNRAS 334: 777-786, 2002

SAHA, A.; CLAVER, J.; HOESSEL, J.G. "Cepheids and Long-Period 
Variables in IC 342" AJ 124: 839-861, 2002

SAHAI, R.; BRILLANT, S.; LIVIO, M.; GREBEL, E.K.; BRANDNER, 
W.; TINGAY, S.J.; NYMAN, L.-A. "Proper Motions in the Knotty, 
Bipolar Jet in Henize 2-90" ApJ 573: L123-L127, 2002

SANCHEZ CONTRERAS, C.; SAHAI, R.; GIL DE PAZ, A. "Physical 
Structure of the Proto-planetary Nebula CRL 618. I. Optical 
Long-Slit Spectroscopy and Imaging" ApJ 578: 269-289, 2002

SANCHEZ-LAVEGA, A. "Observations of Saturn's Ribbon Wave 14 
Years after Its Discovery" Icarus 158: 272-275, 2002

SAND, D.J.; TREU, T.; ELLIS, R.S. "The Dark Matter Density 
Profile of the Lensing Cluster MS 2137-23: a Test of the 
Cold Dark Matter Paradigm" ApJ 574: L129-L133, 2002

SANTIAGO, B.; KERBER, L.; CASTRO, R.; DE GRIJS, R. "On the 
Nature of a Secondary Main-Sequence Turn-Off in the Rich LMC 
Cluster NGC 1868" MNRAS 336: 139-150, 2002

SCHINNERER, E.; MACIEJEWSKI, W.; SCOVILLE, N.; MOUSTAKAS, 
L.A. "Toward the Secondary Bar: Gas Morphology and Dynamics 
in NGC 4303" ApJ 575: 826-844, 2002

SCHMIDT, G.D.; HINES, D.C.; SWITH, S. "The Nascent Bipolar 
Nebula Surrounding the Carbon-rich Variable CIT 6: Transition 
to Axisymmetry" ApJ 576: 429-444, 2002

SCHMITT, H.R.; PRINGLE, J.E.; CLARKE, C.J.; KINNEY, A.L. 
"The Orientation of Jets Relative to Dust Disks in Radio 
Galaxies" ApJ 575: 150-155, 2002

SCHULTE-LADBECK, R.E.; HOPP, U.; DROZDOVSKY, I.O.; GREGGIO, 
L.; CRONE, M.M. "The Oldest Stars of the Extremely Metal-Poor 
Local Group Dwarf Irregular Galaxy Leo A" AJ 124: 896-914, 2002

SIMARD, L.; WILLMER, C.N.A.; VOGT, N.P.; SARAJEDINI, V.L.; 
PHILLIPS, A.C.; WEINER, B.J.; KOO, D.C.; IM, M.; ILLINGWORTH, 
G.D.; FABER, S.M. "The DEEP Groth Strip Survey. II. Hubble 
Space Telescope Structural Parameters of Galaxies in the 
Groth Strip" ApJS 142: 1-33, 2002

SIMON-MILLER, A.A.; GIERASCH, P.J.; BEEBE, R.F.; CONRATH, 
B.; FLASAR, F.M.; ACHTERBERG, R.K.; CASSINI CIRS TEAM "New 
Observational Results Concerning Jupiter's Great Red Spot" 
Icarus 158: 249-266, 2002

SIRIANNI, M.; NOTA, A.; DE MARCHI, G.; LEITHERER, C.; 
CLAMPIN, M. "The Low End of the Initial Mass Function in 
Young Clusters. II. Evidence for Primordial Mass Segregation 
in NGC 330 in the Small Magellanic Cloud" ApJ 579: 275-288, 
2002

SMITH, G.P.; SMAIL, I.; KNEIB, J.-P.; DAVIS, C.J.; TAKAMIYA, 
M.; EBELING, H.; CZOSKE, O. "A Hubble Space Telescope Lensing 
Survey of X-ray Luminous Galaxy Clusters -- III. A Multiply 
Imaged Extremely Red Galaxy at z=1.6" MNRAS 333: L16-L20, 2002

SROMOVSKY, L.A.; FRY, P.M. "Jupiter's Cloud Structure as 
Constrained by Galileo Probe and HST Observations" 
Icarus 157: 373-400, 2002

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