18 research outputs found
Review of Issues Associated with Safe Operation and Management of the Space Shuttle Program
At the request of the President of the United States through the Office of Science and Technology Policy (OSTP), the NASA Administrator tasked the Aerospace Safety Advisory Panel with the responsibility to identify and review issues associated with the safe operation and management of the Space Shuttle program arising from ongoing efforts to improve and streamline operations. These efforts include the consolidation of operations under a single Space Flight Operations Contract (SFOC), downsizing the Space Shuttle workforce and reducing costs of operations and management. The Panel formed five teams to address the potentially significant safety impacts of the seven specific topic areas listed in the study Terms of Reference. These areas were (in the order in which they are presented in this report): Maintenance of independent safety oversight; implementation plan for the transition of Shuttle program management to the Lead Center; communications among NASA Centers and Headquarters; transition plan for downsizing to anticipated workforce levels; implementation of a phased transition to a prime contractor for operations; Shuttle flight rate for Space Station assembly; and planned safety and performance upgrades for Space Station assembly. The study teams collected information through briefings, interviews, telephone conversations and from reviewing applicable documentation. These inputs were distilled by each team into observations and recommendations which were then reviewed by the entire Panel
Gaia Universe Model Snapshot : A statistical analysis of the expected contents of the Gaia catalogue
Context. This study has been developed in the framework of the computational
simulations executed for the preparation of the ESA Gaia astrometric mission.
Aims. We focus on describing the objects and characteristics that Gaia will
potentially observe without taking into consideration instrumental effects
(detection efficiency, observing errors). Methods. The theoretical Universe
Model prepared for the Gaia simulation has been statistically analyzed at a
given time. Ingredients of the model are described, giving most attention to
the stellar content, the double and multiple stars, and variability. Results.
In this simulation the errors have not been included yet. Hence we estimate the
number of objects and their theoretical photometric, astrometric and
spectroscopic characteristics in the case that they are perfectly detected. We
show that Gaia will be able to potentially observe 1.1 billion of stars (single
or part of multiple star systems) of which about 2% are variable stars, 3% have
one or two exoplanets. At the extragalactic level, observations will be
potentially composed by several millions of galaxies, half million to 1 million
of quasars and about 50,000 supernovas that will occur during the 5 years of
mission. The simulated catalogue will be made publicly available by the DPAC on
the Gaia portal of the ESA web site http://www.rssd.esa.int/gaia/.Comment: 21 pages, 21 figures, accepted for publication in Astronomy and
Astrophysics, typos corrected in author name