The topics covered include the following: meetings and travel; calibration; GTO Program (Texas); software; subcontractors; and the mini-symposium

Jefferys, William H.

English

NASA Technical Reports Server

NASA-CR-I96263
(NASA-CR-196263) HUBBLE SPACE
TELESCOPE GTO PROGRAM Semiannual
Progress Report No. 6, I Jan. - 30
Jun. 1994 (Texas Univ.) 8 p
N95-13723
Unclas
G3/89 0016380
/il /622//3
/s -87-c
Sixth Semi-Annual Progress Report
NASA Grant NAG5-1603
Hubble Space Telescope GTO Program
Astrometry Science Team
1994 January 1--1994/une 30
Prepared for
Goddard Space Flight Center
Greenbelt, Maryland 20771
University of Texas at Austin
Department of Astronomy
Austin, Texas 78712
July 1994
Principal Investigator
https://ntrs.nasa.gov/search.jsp?R=19950007310 2020-06-16T10:30:22+00:00Z
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2
Meetings and Travel
STAT meetings were held on January 27 in Austin, TX and on 20 April in Charlottesville,
VA.
Benedict attended Servicing Mission Science Working Group meetings at GSFC on
2/17/94 and 5/20/94.
Benedict organized the Astrometry Mini-Symposium, which was held at STScI 21 April
1994.
Benedict attended the AAS Division on Dynamical Astronomy meeting held 28-29 March
1994 in Kingsville, TX. He reported on our Proxima planet search and on a dynamical
study of NGC 4314.
Benedict, McArthur and Wang attended the 184th AAS meeting (Minneapolis, MN) to
present reports on our planet search, software development, and calibration efforts.
Hemenway continued on his "research sabbatical" at the University of St. Andrews, St.
Andrews, Scotland. He maintained his active participation in the HST Astrometry Science
Team and in the observation and reduction of the GTO program with Duncombe to tie the
Hipparcos reference frame to extragalactic objects, as described above.
Hemenway attended a Hipparcos Project meeting in Hamburg at the end of March, where
he presented the current status of the HST program to tie Hipparcos to extragalactic objects.
The presentation was done in collaboration with Mario Lattanzi at STScI. The status of the
reduction of Hipparcos data to the final catalogue was discussed, with a projected
completion of the end of 1995. The HST data must be reduced and provided to the
Hipparcos project in final form by June 1995. JPL has been given the task of making the
final tie solution using all available data types. To this end, we are collaborating with the
JPL personnel to insure that their models adequately take into account the nature of the
HST data. Their models will be such that they can be run with HST data only to compare
our solutions with theirs (See the discussion of Andrew Lalich's Master's Thesis later in
this report.)
Calibration
Benedict continues to monitor the scale stability of HST FGS 3 astrometry with Proxima
Centaufi field monitoring and Long-term Stability Test (LTSTAB) data. Shortly after the
servicing mission we detected a large change in the scale-like parameter, PA. We also
determined that a delta-OFAD would be required to restore our 2 mas-precision astrometry
capability.
Whipple worked primarily on the analysis and modeling of the distortions present in the
FGS. He wrote the proposal for the delta-OFAD calibration that was run on 27 April 1994
and has worked with other members of the Astrometry team on the analysis of these data.
Wang, Whipple, McArthur, and Jefferys are continuing their efforts to derive a time
dependent model for the FGS distortions.
Shelus has been working with HDOS to try to invent a new way of looking at the lateral
color data, which are still puzzling and difficult to understand.
3GTO Program (Texas)
Planetary Co--ion Search
Benedict leads the team's efforts to discover planetary companions orbiting Proxima
Centauri and Bamard's Star. On 4 May 1994, we obtained the last of 48 observation sets
for Proxima Centauri. As of 15 May 1994 we have obtained 13 of 25 total sets for
Barnard's Star.
The Proxima Centauri observations show that the precision of a single observation is at or
below 2 MAS (RSS of x and y) for stars located in the center of FGS 3. Parallax and
proper motion precision are 0.0004 arcsec and 0.0004 arcsec/yr respectively.
Photometric results for the fast 200 days of Proxima Cen monitoring indicated a 40 day
photometric period, likely due to rotational modulation of bright or dark star spots.
Subsequent observations over 400 additional days strongly suggest an 80 day period. A
possible interpretation is that a spot group disappeared from the surface of Proxima Cen.
As for the planet search, with 48 observation sets we continue to f'md a suspicious peak
near 77 days in the periodogram for both the x and y residuals. Until we have exhausted all
possible instrumental and systematic effects, the 77 day variation is only possibly (20-30%
false positive) a planet with mass of Jupiter. Benedict continues groundbased collaborative
efforts to 1) confirm the photometric periodicity of Proxima Cen, and 2) detect radial
velocity variations. These could be as great as + 170 meters per second, should the planet
actually exist.
HST Hipparcos Extragalactic Link Data:
We continue to make observations of the separations between Hipparcos stars and
extragalactic objects with the FGS astrometer. The first observation was made in April,
1993. To date we have obtained 13 GTO and 62 GO observation sets. The data through the
end of 1993 was completely reduced, but will have to be re-reduced with the following
calibration changes when they are available: a time-variable OFAD, including lever arm
drift, a more accurate plate scale, and a cross filter calibration for the neutral density filter.
The data through day 64 of 1994 are partially reduced. The remainder of the 40 GTO hours
allocated to this project are scheduled for Cycle 4, and should produce a significant number
of separation changes (proper motions) at the milliarcsecond level of accuracy. Two
observations of the same pair observed 14 days apart yielded separations within a
milliarcsecond of each other. Dr. E.P. Bozyan of the University of Rhode Island continued
to analyze and characterize the Hipparcos Link FGS data. She finds that bright non-VLBI
and faint (V>16.0) fail acquisition, in general. Analysis by Nelan (prompted by the minor
planet work) indicates that the walkdown length is insufficient to reach the main null of the
S-curve, but gets to the first "dip." For bright objects, the In'st dip is sufficient to trigger
fine lock, but for fainter objects it is not and the target suffers from "scan step limit
exceeded" and is not acquired in fine lock. A change in the uplinked parameters (the course
track-to-free lock bias) will move the walkdown position over the main S-curve null, and
we expect to get lock on our fainter targets.
Preliminary Hipparcos data from 30 month solution.
In the Hipparcos Link Project, we have 87 Hipparcos star-extragalactic object pairs. We
have received preliminary positions and proper motions with milliarcsecond accuracies for
72 of the Hipparcos stars in our list. These data are being used for initial coordinate frame
system solutions and for testing the veracity of the HST data.
4Lalich Thesis
Andrew Lalich, supervised by Duncombe and Hemenway, has been processing the
Hipparcos Link Data. He has also been working on his Master's thesis, with the
expectation of finishing by the summer this year. His main contributions to the programs
include setting up an extensive series macro spreadsheets on the Macintosh to process our
HST data, adding Hipparcos Parallax to the data analysis, adding the FGS plate.s scale as a
parameter to the overall solution, and incorporating extragalactic targets with non-VLBI
positions into the solution for the time variable rotation only. The large positional
uncertainties of non-VLBI targets are removed by considering the separation changes only,
thereby eliminating the errors in position. The computed changes in separation come from
the accurate Hipparcos proper motions.
Hipparcos Plate Scale.
Included in the data for the Hipparcos Tie are observations of two Hipparcos stars in the
Pickle at the same time. The first of these observations, on 1993 day 200, yielded a
separation which coincided with the separation of the Hipparcos stars from the preliminary
Hipparcos reduction data to 0.004 arcseconds, which is entirely consistent with the errors
of both the HST observations and the preliminary Hipparcos data. The separation was of
the order of 275 arcseconds.
Minor Planet Plate Scale
Mailoux and Kloepper ran ephemerides of minor planets 1474 and 1626 for observation
with the FGSs to determine the plate scale of the astrometer FGS 3 to an accuracy of a
milliarcsecond over the length of the pickle. Hemenway, Kloepper, and Mailoux prepared
the proposal for the observation of minor planet 1626 in July. Nelan checked the proposal
and the commanding system to optimize the proposal and the FGS uplink parameters to
give the best chance of success given our current knowledge of the FGSs. Alex Storrs and
others at STScI spent considerable effort to put the proposal into the system in a timely
fashion to be observed in July. The observations are scheduled for July 9/10.
David Lee's Senior Project.
Hemenway supervised the senior project of St. Andrews undergraduate David Lee. The
project was to determine the astrometric capability of the Gregory Telescope in St.
Andrews, with respect to measuring asteroid positions for HST plate scale calibration. Lee
showed that the CCD on the telescope is capable of relative astrometric accuracies of the
order of 0.1 to 0.2 arcseconds, and may be used in the future for astrometric observations
of minor planets. The M35 OFAD data from the FGS astrometer calibration was used in the
study as an astrometric standard region.
Software
McArthur's primary activities have been reduction of the HST data, including maintenance
and improvement of the pipeline. She has also assisted in maintaining GaussFit, as well as
providing OFAD reduction, LTSTAB and Proxima, including special reductions and
statistical analysis services.
McCartney translated the Pickles class library from Smalltalk to C++. Pickles currently has
69 classes of its own plus about 70 from the Power Plant class library. The new version
compiles under Metrowerks C++ compiler and is 70% complete now.
Subcontractors
Lowell Observatory
Franz and Wasserman devoted most of their effort during this semiannual report period to
the reduction and analysis of post-SMOV FGS TRANS data obtained under the following
proposals:
Proposal 4892: Search for duplicity among faint Hyades stars
Thirteen post-SMOV scan sets for eleven targets were analyzed with the use of color-
calibrated single-star transfer functions derived from post-SMOV scans of Hyades
members previously identified as "single." Among these eleven targets we found three
certain "new" binaries and one probable binary yet to be confirmed. The total of certain
detections now stands at 8 binaries among 26 Hyades cluster members examined under this
proposal. Fourteen targets remain to be investigated.
Proposal 5174: Astrometric Companion Search
The aim of this proposal is the direct detection, at visible wavelengths, of astrometric
("unseen"), low mass companions to six nearby M dwarfs. Among four objects observed
during the report period, we have detection, confirmation, and reconfirmation of the
predicted astrometric companion for the following three targets:
5174_1 = BD+67.552
5174_2 = AC+48.1595-89
5174_3 =W922
Other activities during the report period included:
Presentation of a paper on binary star investigations with HST-FGS in the TRANS-mode
at the AAS-DDA meeting at Kingsville, TX.
Presentation at the Minneapolis AAS meeting of a poster paper on the detection of binaries
among faint Hyades cluster members from pre-SMOV TRANS-mode observations.
Preparation (and acceptance) of four abstracts on various aspects of the Faint Hyades
Binary Search for presentations at the ESO Workshop "The Bottom of the Main
Sequence--and Beyond" to be held at Garching 8-10 August 1994, and at the subsequent
IAU General Assembly.
University of Virginia
A few frames on the southernmost targets were taken in early and late January at Siding
Spring Observatory while on two observing runs for a different project.
Considerable time was spent preparing for the STAT presentation at the Space Telescope
Science Institute in April.
In the same time frame and running into May we had to redo the guide star selections for
the six astrophysically interesting targets. This involve remeasuring a few plates and
6enteringthedataintopreexistingPicklesf'des.This madethefinal selectionslesstime
consuming.
Mostof the time during late May and all of June has been spent reviewing research
notebooks in search of binary stars that will yield useful data from HST astrometric
observations. For example, there is a well observed double lined spectroscopic binary of
very early spectral type (O5V+O5V) which may be close enough to yield an orbital parallax
and hence the individual masses. There are no accurate masses for stars of such early types
on the main sequence. A list of 15 possible binary systems has been compiled so far.
Yale University
GTO Globular Cluster Internal Motions
Image reconstruction has been started on the Planetary Camera exposures of M15 by T.
Girard and Y. Li. Reconstruction improves both the detectability and precision of the image
centers. A preliminary exploration of the modeling of the distortion across the PC field was
also made using the multiple, overlapping exposures. Results have been reported on the
67th STAT meeting at STScI on April 21 and the 68th meeting at Austin on July 8,
respectively. A poster paper "Differential Astrometry with the HST Planetary Camera" was
presented at the 184th AAS meeting at Minneapolis in June.
GTO Hyades Cluster Member FGS Parallaxes
The second epoch March observations were made of the Hyades after some last minute
help by our superb technical support friends at the STScI. X. Guo obtained the output data
of the pipeline preprocessing and looked at the behavior of the checking stars and the RMS
of the solutions in both X and Y for each field between the 2nd epoch observations (March
1994) and the 1st epoch observations (September 1993). On the checking stars, positional
drifts of different check stars in a same field are some time inconsistent. The difference is
probably caused by time and position dependent errors. We have to look into the coordinate
drift issue in detail in future. The typical RMS is about +8 MAS, while the Y solutions
seem to be better than the X solutions. Since the solutions are between two epochs before
and after the servicing mission and the OFAD is different, we will look at the RMS again
when the revised OFAD is installed in the pipeline.
GTO Parallel Observations
A catalogue of the GTO Parallel observations made with the HST WFC continues to be
archived at Yale by Graduate student R. Mendez.
Fixed Head Star Trackers
Work on the FI-IST Waffles Catalogue has continued with the goal of improving the
accuracy of the data in the catalogue and removing the duplicate entries. Research Assistant
Y. Li has removed the duplicate entries in the catalogue, and replaced all of the existing data
with improved accuracy data where available. D. Hoffleit and Research Assistant R.
Koopmann are examining in detail several thousand probable duplicate entries to determine
if they are duplicates entries or separate stars. The positions and proper motions in the
FHST Catalogue have been replaced in order of preference by data from the FK5 and
Supplement, IRS, ACRS and PPM, while the magnitudes, colors and spectral types have
been updated with data from the Hipparcos Input Catalog and new UBV photoelectric
photometry. A new release is being prepared for inclusion in J. McCarmey's Waffles
program. Y. Li also improved the Annex file which mainly contains information on the
7duplicity and variability of stars in the Catalogue with the WDS (of the latest version) and
GCVS, NSV.
Mendez has successfully expanded his model of the Galaxy to compute the brightness
distribution at low galactic latitudes. The data will be used to search for coincidences in the
failure of the FHST as a function of the integrated brightness of the background. Great
effort was made to improving the algorithms and data base for dealing with interstellar
reddening and absorption, both of which are critically important in the galactic plane. 6 low
Galactic latitude GSC plates were extracted to test his model. At least for 5 plates, the
prediction in star count of model to observation is very good, while the remaining one
might have a problem in measurement due to crowdedness.
Hipparcos Link to the Extragalactic Reference Frame
At the request of the Hipparcos Project, we have undertaken to establish the preliminary
Hipparcos link to the groundbased absolute proper motions with respect to galaxies. The
Lick Observatory Northern Proper Motion program and Yale-San Juan Southern Proper
Motion Program data will be combined to yield about 6000 NPM and 1000 SPM absolute
proper motions of Hipparcos stars. Upon receipt of the Hipparcos data, I. Platais and T.
Girard started to rereduce our SPM data in about 1000 square degrees around the South
Galactic Pole in order to better define the plate constants. Use of the remarkably accurate
Hipparcos positions has allowed us to determine the higher order plate constants with
greater confidence and that should result in more systematically correct absolute proper
motions. The absolute proper motions derived from those improved plate constants will
then be used to establish the Hipparcos link to the groundbased absolute proper motions
with respect to galaxies.
The Mini-symposium
The team presented on 21 April 1994 a series of brief reports of work in progress to many
of the people who have over the years enabled astrometry with HST. Here is a list of those
reports.
Astrometry with Hubble Space Telescope
A mini-Symposium
Space Telescope Science Institute Auditorium
21 April 1994
1:30-4:30 PM
FGS Performance Characteristics
Plate Scale Status Report
Maintaining the Astrometric Calibration of FGS #3
Millisecond of arc double star astrometry with HST
Incidence of Duplicity in the Hyades
Crowded field Astrometry with an HST Fine Guidance Sensor
Astrometry with the HST Planetary Camera
The HIPPARCOS/Extragalactic Tie-in: Status Report
Parallaxes of Astrophysically Interesting Objects---
The Six we Picked and Why
HST: A Generator of sub-millisecond of arc Parallaxes
A Planetary Companion to Pmxima Centauri: Status Report
Poster: GaussFit--a Modeler's Tool
Poster : Pickles--a Graphical Observation Planning Tool
E. Nelan and D. Story
M. Lattanzi and L. Taft
W. Jefferys and G. Benedict
O. Franz
O. Franz
M. Lattanzi and L. Taff
T. Girard and Wm. van Altena
R. Duncombe and P. Hemenway
L. Fredrick
G. Benedict
G. Benedict
B. McArthur
J. McCarmey


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