Re: Does Hubble have to die?

The following is a link to the second phase of a study to determine the
distances to the pleiades open star cluster (tight star cluster visible
in are fall night sky), and refining the accuarices of some of the
observed binaries systems to support or clarify some results from the
hipparcus project.


http://www.stsci.edu/observing/phase2-public/8777.pro

"1.Proposal Title:
Calibrating Stellar Models with the Pleiades: Resolving the Distance
Discrepancy- Cycle9

5. Abstract
This is the second phase of a multi-year effort to measure an accurate
distance to the Pleiades and to resolve the problem raised by the
Hipparcos results for this cluster. The Hipparcos distance, taken at
face value, indicates that solar- composition ZAMS stars are 30%
fainter than previously believed. The resolution to the Hipparcos
distance problem is vital for understanding all the parallaxes that
have come from that mission and hence this issue is fundamental to the
cosmic distance scale. In this first phase we observed several
spectroscopic binary systems with 2 to 3 year orbital periods to
assertain our prospects for deriving visual orbits and hence orbital
parallaxes for these cluster members. Although the FGS did resolve some
of the systems, it became clear that the accuarcies that would result
would not be sufficient to either confirm or refute the Hipparcos
result. In this phase, we have changed our strategy to use the FGS to
directly determine trigonometric parallaxes for 8 (or more) Pleiads.
The accuracy of our measured parallaxes, expected to have sigma < 0.3
mas, will be sufficient to resolve the Hipparcos distance discrepency,
and will allow us to directly determine the absolute magnitude for the
ZAMS stars in our sample without the additional uncertainties
introduced by effects of the cluster's depth.

Observations Description
Target Selection: The best targets for this study are stars with a high
probability of being cluster members, with no indication of binarity,
and in a region of sky such that two or more fall within the FGS field
of view (FOV) for a given HST pointing and ORIENT within off-nominal
roll constraints at times of maximum parallax factor. We also require
that 7 or more non-cluster members fall within the FOV, so that a
sufficient number of reference stars are available for us to determine
an accurate relative parallax as well as a statistically accurate
conversion of relative to absolute parallax. We have identified 7
Pleiads for this project, H3179, H3063, H3038 for "pointing 1", H263,
H193, and H134 for "pointing 2", and H915 and H923 for "pointing 3".
Pointing 1 has 10 non-cluster reference stars, pointing 2 has 8, and
pointing 3 has 9. Given that the cluster has a large proper motion
(+20,-44) mas/yr in (R.A., Dec), it will be easy to deterine if any of
the reference stars are actually cluster members, but it will also be
necessary to observe these fields through at least two paralliptic
epochs, i.e., over the next two years. We have been allocated 9 HST
orbits in each of cycles 9 and 10, and have an unused reserve of 2 HST
orbits from cycle 8, for a total of 20 HST orbits. We plan to observe
each of the three fields with two visits at times of maximum parallax
factor in Aug 2000 and Feb 2001, and then one visit per field in Aug
2001, Feb 2002, and one visit for each of two fields in Aug 2002, for a
total of 20 HST orbits. In each visit the cluster members and reference
stars will be observed several times by FGS1r in Position Mode with the
F583W filter while FGS2r and FGS3 maintain finelock on guide star
pairs."

Authors
PI: David Soderblom Space Telescope Science Institute
CoI: Dr. Lawrence Wasserman Lowell Observatory

CoI: Dr. Fritz Benedict Univ. Texas

CoI: Dr. Otto Franz Lowell Observatory

CoI: Dr. Todd Henry Georgia State University

CoI: Dr. Burton Jones Lick Observatory

CoI: Dr. David Latham Harvard-Smithsonian Center
Astrophysics
CoI: Dr. Jean-Claude Mermilliod Geneva Obs.

CoI: Dr. Ed Nelan Space Telescope Science
Institute
Dr. Marc Pinsonneault Ohio State Univ Stauffer
Harvard-Smithsonian . CoI: Dr. John
Center for Astrophysics
CoI: Dr. Guillermo Torres Harvard-Smithsonian Center for
Astrophysics"

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understanding of the universe around us.
Tom




columbiaaccidentinvestigation wrote:
The following study of the hyades star cluster is based on utilizing
the hubbles fine guidance sensors to refine our understanding of
stellar distances and motions in order to determine an open star
clusters the center point of origin. (in this case a study of the the
stars comprising hyades cluster the v shaped cluster in our fall night
sky above orion).

http://www.journals.uchicago.edu/ApJ/journal/issues/ApJL/v486n2/5359/5359..pdf


THE DISTANCE TO THE HYADES CLUSTER BASED ON HUBBLE SPACE TELESCOPE FINE
GUIDANCE SENSOR PARALLAXES

"ABSTRACT
Trigonometric parallax observations made with the Hubble Space
Telescope (HST) Fine Guidance Sensor FGS) 3 of seven Hyades members in
six fields of view have been analyzed along with their proper motions
to determine the distance to the cluster. Knowledge of the convergent
point and mean proper motion of the Hyades critical to the derivation
of the distance to the center of the cluster. Depending on the choice
of the proper-motion system, the derived cluster center distance varies
by 9%. Adopting a reference distance of 46.1 pc 2 M 5 3.32, which is
derived from the ground-based parallaxes in the General Catalogue of
Trigonometric Stellar Parallaxes (1995 edition), the FK5/PPM
proper-motion system yields a distance 4% larger, while the Hanson
system yields a distance 2% smaller. The HST FGS parallaxes reported
here yield either a 14% or 5% larger distance, depending on the choice
of the proper-motion system. Orbital parallaxes (Torres et al.) yield
an average distance 4% larger than the reference distance. The
variation in the distance derived from the HST data illustrates the
importance of the proper-motion system and the individual proper
motions to the derivation of the distance to the Hyades center;
therefore, a full utilization of the HST FGS parallaxes awaits the
establishment an accurate and consistent proper-motion system. Subject
headings: astrometry-stars: distances-stars: fundamental
parameters"

authors
"W. F. VAN ALTENA, C. -L. LU,1 J. T. LEE, T. M. GIRARD, X.GUO, C. P.
DELIYANNIS,2 I. PLATAIS, AND V. KOZHURINA-PLATAIS Yale Astronomy
Department, New Haven, CT 05620

B. MCARTHUR, G. F. BENEDICT, R. L. DUNCOMBE, P. D. HEMENWAY,3 W. H.
JEFFERYS, J. R. KING,2,4 E. NELAN,4 P. S. SHELUS, D. STORY, AND A.
WHIPPLE5 University of Texas at Austin, Austin, TX 78712

O. G. FRANZ AND L. WASSERMAN Lowell Observatory, Flagstaff, AZ 86001

L. W. FREDRICK Astronomy Department, University of Virginia,
Charlottesville, VA 22903

R. B. HANSON, A. R. KLEMOLA, AND B. F. JONES Lick Observatory, Santa
Cruz, CA 95064

R. M´ENDEZ European Southern Observatory, Karl-Schwarzschild-Strasse
2, D-85748, Garching bei

Mu¨nchen, Germany W.-S. TSAY
Institute of Astronomy, National Central University, Chun-Li, Taiwan
32054
AND A. BRADLEY

Allied Signal Corporation, P. O. Box 91, Annapolis Junction, MD 20701
Received 1997 May 16; accepted 1997 June 25"



Open sharing of information is crucial to improving everybody's
understanding of the universe around us.
Tom



columbiaaccidentinvestigation wrote:
The HST's Fine Guidance Sensors have a tremendous potential to carry
out a focused astrometric research program after the next servicing
mission (near 2013) , and given the fact the next generation space
telescopes (james web, and sim, space telescopes) technology has yet to
proven reliable, it would be logical to plan for an extended retasked
mission utililizing the hubble platform to conduct science as long as
possible.

http://www.stsci.edu/hst/fgs/documents/papers/spie.pdf

The Fine Guidance Sensors Aboard the Hubble Space Telescope, the
Scientific Capabilities of these Interferometers Edmund Nelana, Olivia
Lupiea, Barbara McArthurb, G. Fritz Benedictb, Otto Franzc, Larry
Wassermanc, Linda Reedd, Russ Makidona, Lauretta Nagela, a Space
Telescope Science Institute, Baltimore M, b University of Texas at
Austin, Austin Texas, c Lowell Observatory, Flagstaff, Az, d Raytheon,
Danbury Ct.
"ABSTRACT
The Fine Guidance Sensors (FGS) aboard the Hubble Space Telescope (HST)
are optical white light shearing interferometers that offer a unique
capability to astronomers. The FGSs's photometric dynamic range,
fringe visibility, and fringe tracking ability allow the instrument to
exploit the benefits of performing interferometry from a spacebased
platform. The FGSs routinely provide HST with 2 milli-seconds of arc
pointing stability. The FGS designated as the Astrometer, FGS3, has
also been used to (1) perform 2 mas relative astrometry over the
central 4 arc minutes of its field of view, (2) determine the true
relative orbits of close (20mas) faint (mv=15) binary systems, (3)
measure the angular diameter of a giant star, (4) search for
extra-solar planets, (5) observe occultations of stars by solar system
objects, as well as (6) photometrically monitor stellar flares on a low
mass M dwarf. In this paper we discuss this unique instrument, its
design, performance, and the areas of science for which it is the only
device able to successfully observe objects of interest...

6. CONCLUSIONS
The Hubble Space Telescope's FGS astrometry program offers
astronomers the means to measure the parallax and
proper motions of objects as faint as mv = 16 over several arc minute
fields with accuracies often better than 2 mas. The FGS can also
resolve the components of faint (mv= 15) binary systems with magnitude
differences as large as 3 and separations as small as 20 mas (and less
with FGS1R) at an accuracy of about 1 mas. By simultaneously observing
binary systems in TRANSFER mode along with reference stars in POSITION
mode, the observer can determine the true relative orbit as well as
measure the object's parallax. With these data, the system's total
mass can be determined. If the astrometry is of sufficient quality, the
motion of each component about the system's barycenter can be
measured, which in turn, yields the relative masses. When this is
coupled with the photometric data, the mass to luminosity ratio of each
component becomes known. This technique has been successfully applied
to observe a low mass binary system9. On the other hand, if a double
lined spectroscopic binary (a two component radial velocity object) is
observed with the FGS in Transfer mode at an adequate number of points
along its orbit, then the true parallax of the object can be determined
without needing to resort to positional astrometric measurements. No
imaging device is available to study the small separation binary
systems observable by the FGS. The ground based long baseline
interferometers can resolve objects where even the FGS would fail, but
only if the object is bright (mv<6) or is within (typically) 30" of a
bright star (for active fringe tracking). Speckle interferometry can
observe objects as faint as mv=11 but provides no differential
photometry and cannot resolve structure below 30 mas (even then, not
with the 1mas accuracy of the FGS). Even with the expected advances in
ground based long baseline interferometers (e.g., Keck, VLTI)11, it
appears that the FGS will be unchallenged as the only instrument
available for the study of binary systems fainter than about mv = 8 and
separations less than 40 mas. This, along with its ability to
simultaneously provide 1-2 mas relative astrometry for these objects,
provides the FGS with a niche occupied solely by itself, probably until
the arrival of the long baseline interferometers in space, such as SIM
in 2005."


Open sharing of information is crucial to improving everybody's
understanding of the universe around us.
Tom



columbiaaccidentinvestigation wrote:
The following is a clip from the Arizona university website describing
the hipparcus satellite, which has made one of the greatest star
catalogues to date. Now if we could utilize hubbles last years for
stellar distance observations or astrometric data gathering, by
boosting it to a more elliptical orbit, and re-tasking the software,
the hst could gather stellar distance data for years to come.

http://ircamera.as.arizona.edu/NatSci102/images/exthipparchos.html

"Hipparcos was given a wonderful legacy, its Input Catalogue,
endowing it with the then best of ground astrometric data. From launch
late in 1989 to mid-1993, the satellite watched the sky. The first
processed results began to appear in the spring of 1997, for each star
sighting took meaning only after elaborate comparisons with many
others.
Four distinct teams--hundreds of astronomers, engineers and data
mavens--worked long at the task. They had been confronted by a sudden,
daunting failure on launch; the rocket did not put Hipparcos into the
planned geostationary orbit. As Earth then turned beneath Hipparcos, no
single ground station could collect the day's stream of data beaming
downward by radio. Quickly, however, not one but three ground stations
were set up around the world. In the end two thirds of all expected
data came in, a triumph of masterful salvage in space.
How does it work? The satellite scanned the sky as it orbited, spinning
on its viewing axis. Its long, elliptical Earth orbits took 10 hours,
sampling stars in a belt about a degree wide in the sky. Meanwhile the
auxiliary star-mapping detectors picked up catalogued guide stars to
find approximately where the axis pointed and thus to identify which
stars were being seen. Every star signal that entered the optics
crossed a couple of thousand slits in the main electronic sensors as
the probe spun, the light registering as voltage pulses. Individual
stars generated long strings of pulses over time--some 2,000 stars
during each 10-hour orbit."

Open sharing of information is crucial to improving everybody's
understanding of the universe around us.
Tom


columbiaaccidentinvestigation wrote:
Jeff Findley wrote: "Because the shuttle will be retired in 2010 and
Hubble will likely be doing good science at that time because of the
newly scheduled servicing mission. Even if NASA wanted to pay for the
last shuttle mission in 2010 to retrieve Hubble, why bring back Hubble
when it's still doing good science? None of this makes sense. The
desire to bring Hubble back and stick it into
a museum is an emotional one, not a rational one."

One possible idea for Hubble, would be to do as the Hipparcos team did
when it's satellite developed problems, the satellite was utilized to
calculate stellar distances by parallax. The best place for Hubble is
to stay is in space, this would place no risk to crew and vehicle on a
return mission, and if we can somehow extend out it's life span by
boosting/reprogramming the space telescope to a highly elliptical
orbit, and conduct short observations for the purposes of measuring
stellar distances by parallax we could utilize the great observatory
for more science as the telescope was intended to do, and not collect
dust sitting in a museum. This re-boost/reprogramming and re-tasking
could maybe have the HST (one of the greatest observatories ever made),
conduct one last long data collection mission and that is accurately
measuring stellar distances.

The following link is from the Sloan digital survey site, describing
parallax and Hipparcos's contributions.
http://cas.sdss.org/dr5/en/proj/advanced/hr/hipparcos1.asp


Open sharing of information is crucial to improving everybody's
understanding of the universe around us.
Tom

.

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