Status Report

NASA Hubble Space Telescope Daily Report #4794

By SpaceRef Editor
February 21, 2009
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Continuing to collect World Class Science

PERIOD COVERED: 5am February 18 – 5am February 19, 2009 (DOY 049/1000z-050/1000z)


ACS/SBC 11984

Observing Saturn’s High Latitude Polar Auroras

Planetary auroral emissions are critical indicators of how the magnetospheres of the planets work. Recently, a new component of Saturn’s auroral emissions, i.e. high latitude auroras inside the main auroral oval, have been observed by the Cassini spacecraft during otherwise quiet auroral conditions. Such high latitude auroras are of immense interest since they occur on magnetic flux tubes connected to a region that is key to the overall dynamics of the system, the magnetotail, and where if conventional theories regarding Saturn’s magnetosphere are correct there should not be any auroras. These faint auroral emissions have not been previously observed by the Hubble Space Telescope (HST). However, the unique oblique viewing geometry afforded during early 2009 due to Saturn’s orbital longitude will result in the apparent brightening of these polar emissions due to the limb-brightening effect, with the result that they may be observable by HST for the first ever time. In addition, at this time the Cassini spacecraft will be in a high latitude orbit, with a trajectory that will take it through these magnetic flux tubes, providing essential simultaneous in situ data. This is the last time Cassini will be in such an orbit during its mission as currently scheduled and HST is the only instrument capable of obtaining sustained long-term observations of Saturn’s auroras. These observations will address the following:

Does Saturn exhibit high latitude UV auroras observable by HST? Where do these auroras occur, and at what altitude? How do these auroras behave over time? How variable are they? Are they periodic? How do they behave with respect to other auroral components? What processes drive these auroras?

Are these auroras generated by processes internal to the magnetosphere or are they driven by the solar wind? How do the infrared (IR) auroras relate to the ultraviolet (UV) auroras?

WFPC2 11797

Supplemental WFPC2 CYCLE 16 Intflat Linearity Check and Filter Rotation Anomaly Monitor

Supplemental observations to 11029, to cover period from Aug 08 to SM4. Intflat observations will be taken to provide a linearity check: the linearity test consists of a series of intflats in F555W, in each gain and each shutter. A combination of intflats, visflats, and earthflats will be used to check the repeatability of filter wheel motions. (Intflat sequences tied to decons, visits 1-18 in prop 10363, have been moved to the cycle 15 decon proposal 11022 for easier scheduling.)

Note: long-exposure WFPC2 intflats must be scheduled during ACS anneals to prevent stray light from the WFPC2 lamps from contaminating long ACS external exposures.

Note: These are supplemental observations to cover June to SM4 (Oct 8 ’08) + 6 months.

WFPC2 11944

Binaries at the Extremes of the H-R Diagram

We propose to use HST/Fine Guidance Sensor 1r to survey for binaries among some of the most massive, least massive, and oldest stars in our part of the Galaxy. FGS allows us to spatially resolve binary systems that are too faint to observe using ground-based, speckle or optical long baseline interferometry, and too close to resolve with AO. We propose a SNAP-style program of single orbit FGS TRANS mode observations of very massive stars in the cluster NGC 3603, luminous blue variables, nearby low mass main sequence stars, cool subdwarf stars, and white dwarfs. These observations will help us to (1) identify systems suitable for follow up studies for mass determination, (2) study the role of binaries in stellar birth and in advanced evolutionary states, (3) explore the fundamental properties of stars near the main sequence-brown dwarf boundary, (4) understand the role of binaries for X-ray bright systems, (5) find binaries among ancient and nearby subdwarf stars, and (6) help calibrate the white dwarf mass – radius relation.

WFPC2 11978

Luminous and Dark Matter in Disk Galaxies from Strong Lensing and Stellar Kinematics

The formation of realistic disk galaxies within the LCDM paradigm is still an unsolved problem. Theory is only now beginning to make predictions for how dark matter halos respond to galaxy formation and for the properties of disk galaxies. Measuring the density profiles of dark matter halos on galaxy scales is therefore a strong test for the standard paradigm of galaxy formation, offering great potential for discovery. However, from an observational point of view, the degeneracy between the stellar and dark matter contributions to galaxy rotation curves remains a major road block. Strong gravitational lensing, when coupled to spatially-resolved kinematics and stellar population models, can solve this long-standing problem. Unfortunately, this joint methodology could not be exploited so far due to the paucity of known edge-on spiral lenses. Exploiting the full SDSS-DR7 archive we have identified a new sample of exactly these systems. We propose multi-color HST imaging to confirm and measure a sample of twenty spiral lenses, covering a range of bulge to disk ratios. By combining dynamical lensing and stellar population information for this unique sample we will deliver the first statistical constraints on halos and disk properties, and a new stringent test of disk galaxy formation theories.

WFPC2 11989

The Integral Sign Galaxy

We will observe the unusual warped disk galaxy known as the Integral Sign Galaxy, UGC 3697, with a small two-position WFPC2 mosaic. Observations will be obtained in three broad band filters and the resulting image will be released on the 19th anniversary of the launch of the Hubble Space Telescope on ~April 24, 2009. Multidrizzled mosaics will be made available through the archive.


Significant Spacecraft Anomalies: (The following are preliminary reports of potential non-nominal performance that will be investigated.)


11684 – REAcq (2,1,2) failed to RGA Hold due to (QF2STOPF) stop flag on FGS-2 @ 049/1523z

Observations affected: WFPC Proposal ID# 11978 observations 85-88.

11685 – REAcq (1,3,3) failed to RGA Hold due to (QF1STOPF) flag on FGS-1 @ 049/1908z

Observations affected: WFPC Proposal ID# 11989, observations 91 & 92.

11686 – REAcq (1,3,3) fails to Gyro Control, V1 error was too large to correct @ 049/2121z

Observations affected: WFPC Proposal ID# 11989, observations 93 & 94.

11687 – REAcq (1,3,3) failed to RGA Hold due to (QF1STOPF) flag on FGS-1 @ 049/2200z

Observations affected: WFPC Proposal ID# 11989, observations 95 & 96.



                         SCHEDULED      SUCCESSFUL

FGS GSacq                06                   06
FGS REacq                08                   04
OBAD with Maneuver       28                   28


SpaceRef staff editor.