Hubble performance on-orbit

A summary of the Hubble Space Telescope (HST) nickel-hydrogen (NiH/sub 2/) battery performance from launch to the present. Over the life of HST vehicle configuration, charge system degradation and failures, together with thermal design limitations, have had a significant effect on the capacity of HST batteries. Changes made to the charge system configuration to protect against power system failures and to maintain battery thermal stability resulted in undercharging of the batteries. This undercharging resulted in decreased usable battery capacity as well as battery cell voltage/capacity divergence. This cell divergence was made evident during on-orbit battery capacity measurements by a relatively shallow slope of the discharge curve following the discharge knee. Early efforts to improve battery performance have been successful. On-orbit capacity measurement data indicates increases in the usable battery capacity of all six batteries as well as improvements in the battery cell voltage/capacity divergence. Additional measures have been implemented to improve battery performance, however, failures within the HST Power Control Unit (PCU) have prevented verification of battery status.     

M. Livio, S. M. Fall and P. Madau (eds.), The Hubble Deep Field, Space Telescope Conference Series 11

The proceedings of a conference dealing with only one piece of observational activity: the deepest optical image obtained by the HST during a 150 orbit observational program. The main result, presented in several papers, is that we are now able to witness the period of galaxy formation. Very readable too is Allan Sandage's historical review, being the introductory paper to the meeting. This revised version was published online in August 2006 with corrections to the Cover Date.     

Hubble Space Telescope solar array change-out, mission anomaliesand returned flight hardware

During the successful First Servicing Mission on the Hubble Space Telescope the two solar arrays were replaced with new and improved solar arrays. An electrical short and four solar array mechanical system anomalies occurred: (1) the upper outer bistem on the +V2 wing had developed kinks and then failed to retract; (2) additional friction between the solar array latch fitting and the aft latch berthing microswitch guard probably caused the failure of the primary deployment mechanism to deploy the solar array wings; (3) the secondary deployment mechanism retract limit microswitch activation is believed to be a result of the dynamic motion of the wings during the retraction event. Successful retraction took place after five attempts; and (4) additional torques induced during extra vehicular activity, flight support system and orbiter activities caused the wings to move from the latching destination. The physical appearance and durability of the materials on the solar array and the physical position of hardware indicators were investigated at Kennedy Space Center after the flight servicing mission. Evidence of micrometeoroid damage and the darkened silicone coatings were apparent. Isolation and continuity tests confirmed the location of shorts which occurred during the First Servicing Mission     

Hubble Space Telescope at twelve years of age

The Hubble Space Telescope was deployed from the Space Shuttle Discovery into a 380-mile high Earth orbit on April 25, 1990. It subsequently made outstanding astronomical discoveries with its 8-foot (2.4-meter) telescope and other scientific instruments. Critical to the successful observations was continuous availability of power from its solar arrays during sunlit periods, and from nickel-hydrogen batteries when the satellite was in the Earth's shadow. The adopted nickel-hydrogen batteries were carefully selected and tested to confirm their depth-of-discharge and operating temperature that delivered the longest life in charge/discharge cycling service. These batteries had a design life of 7 years. At 12 years after launch the Hubble batteries have delivered more charge/discharge cycles than any other batteries in low-Earth orbit. However, the Hubble batteries have been subjected to many unexpected stresses, and peculiar reductions in battery capacity have been observed. Battery replacement requires a costly trip to the Hubble Space Telescope by astronauts, so the remaining useful life of the batteries must be predicted. Already in four servicing missions, astronauts have replaced or modified optics, solar arrays, a power control unit, and various science packages. A fifth servicing mission is scheduled in 2004. This paper discusses battery charging hardware and software controls, history of battery events in Hubble, cell performance model and spare battery tests, and capacity walkdown.     

Hubble Space Telescope Observations of Nebular Morphologies and Their Implications

The morphologies of nebulae, as revealed by HST observations are presented. Mechanisms for the formation of axisymmetric and point-symmetric nebulae are reviewed. Critical observations that can test the models presented in this paper are suggested.     

What we have not learned from the troubles with the Hubble

The Hubble space-based telescope is a great tribute to our progress in space. The ability to place an optical telescope at a significant distance from the Earth's surface, away from the interference of the planet's unsteady atmosphere, have already paid off by producing magnificent records of astronomical activities in the depths of outer space. In the past the problems with the alignment of the Hubble's optics were blamed on the manufacturers of it's optical components. The hastily set investigation concluded that the problem is a spherical aberration of the primary mirror (the primary mirror is said to be 2 microns too flat at the edges). It is suggested that the real culprit is the Parker Effect. Since the time of Galileo Galilei, all telescopes were built, aligned, and used on the Earth's surface. Hubble is the first telescope to be built and aligned on Earth for use in space. Because of this we have to consider the fundamental differences between the alignment of surface-based and space-based telescopes. For those who missed our article “The Parker Effect and Navigation in Space” published in the January issue. The Parker Effect describes the result of interaction between inertial bodies (anything that has mass) and non-inertial media (light or other E/M fields)     

Kitchin,C. R., Astrophysical Techniques

Space Science Reviews -     

经验与启示——张镇中教授谈麦道公司的沉没以及中美MD-82合作项目

张镇中教授亲历了美国麦道公司由盛到衰的过程，同时作为麦道公司的总代表，发起并参与了在上海总装MD-82飞机的中美合作项目，尽管这个计划的结果并不如人意，但它却是我国大飞机发展历程中一个重要的事件。前不久我们对张镇中教授进行了专访，请他回忆了这段经历，并对我国大飞机发展提出了一些看法和建议。     

C. M. Carollo,H. C. Ferguson and R. F. G. Wyse (eds.), The Formation of Galactic Bulges

Space Science Reviews -     

Hubble Space Telescope spectroscopy of massive hot stars in the Magellanic Clouds and M31

Using the Hubble Space Telescope (HST) and the Faint Object Spectrograph (FOS) high signal to noise spectrograms were obtained for 15 OB stars in the Magellanic Clouds^***, three of which are of spectral type O3. The data cover the spectral region from 1150 A – 2300 A with a resolution of /1 A. One O8.5 supergiant, OB78#231, in M31is also included in this work. These data are a substantial improvement on previous high resolution IUE observations in the Magellanic Clouds (Walborn et al. 1985 and references therein) because of the smaller aperture and the much better signal to noise ratio, while no high resolution UV spectra of O stars in M31 have been obtained before. In this paper we discuss various morphological aspects of the spectra, concerning metallicity and the stellar winds, compared to galactic analogues.     

在B.C.钓螃蟹

<正>在加拿大不列颠哥伦比亚省(B.C.省)的内陆平原,一年四季都是捕蟹的好时节。从早到晚,你随时都可以去抓螃蟹,甚至还可以在天黑的时候或者半夜去。在加拿大不列颠哥伦比亚省(B.C.省)的内陆平原,一年四季都是捕蟹的好时     

Comments on, `Improved multilevel quantization for detection ofnarrowband signals' by C.W. Helstrom

It is shown that optimum quantization levels may be obtained by using C.W. Helstrom's approach of the above named work (see ibid., vol.AES-24, p.141-147, Mar. 1988) but maximizing exact detection probabilities instead of approximations to it if the moment generating function of the test statistic can be expressed in rational form. Adaptive levels may be obtained for the quantizers by cell averaging, leading to constant false alarm rate (CFAR) detectors