Over 1 million spectra have been obtained by LAMOST telescope during its Pilot Survey, of which half million
spectra are released. LAMOST 1D pipeline was designed to classify spectra, measure redshift, and estimate
parameters. Data quality is a key factor that affect the results of our reduction. For high signal-to-noise(S/N)
spectra, which have good qualities, the software shows a reasonable performance on not only the spectral classification but also the redshift measurement. For bad quality data, the software lost its stability and precision.
Human check is adopted into our spectra processing and final data release. By calculate the confidence of our
redshift measurement, we assess the correction of our redshift measurement and recalculate the low confidence
redshift for data release.
A LAMOST survey observation plate should have a bright star in the center for Shack-Hartmann wave front
estimation. Given the plate position, there should be at least one proper guide star on each guide CCD after
a small angle focal plate rotation. The detailed requirements vary according to different observation condition.
As a consequence, the plate center cannot be placed arbitrarily. Using the HIPMAIN star catalog as the
initial candidates and the USNO-B1.0 catalog for neighbor star reference, several lists of acceptable survey plate
centers are generated for different observation conditions. The sky area coverage is tested with each plate list.
Tiling algorithms using these finite plate centers are optimized for the purpose of evenly sampling and catalog
completeness. The tiling is much easier for dark nights than bright nights as there are more optional plate
centers. The result is applied in the LAMOST pilot survey for verification and feedback is used to update the
An adaptive algorithm is presented for extracting the flux of the fiber spectrum from a two-dimensional
image observed by LAMOST (Large Sky Area Multi-Object Fiber Spectroscopic Telescope). The new
algorithm is based on RBF (Radial basis function) neural network, employing the Gaussian basis
function to approximate the profile of the spectrum in the spatial direction. In this study, an experiment
is performed with the simulated data. The experimental results show that the new algorithm can highly
enhance the computing speed while preserving the accuracy in the flux extraction. A feasible approach
is thus offered for extracting the flux of the fiber spectrum for LAMOST.
The 4 m large aperture, 5 degrees field of view and 4000 fibers make LAMOST an important optical
spectrum astronomical telescope in the world. It will take a survey observation on about 10,000,000
stars in 20,000 square degrees field of view of north celestial sphere within several years. In order to
fully utilize the advantages of a large number of goal optic fibers of LAMOST, carry out the survey
observation with better efficiency, and economize valuable astronomical observation time, it is very
essential and worthy to make a series of observation plans with utilization ratio of optic fiber as high as
possible, which is exactly the scientific goal of Survey Strategy System (SSS) of LAMOST. Various
kinds of static and dynamic restraint conditions affecting a survey observation are analyzed and
modeled. On the basis of looking for tile with the largest density, the Mean-Shift algorithm is adopted,
effectively improving the utilization ratio of optic fiber. With the progress of LAMOST project, new
restraints and algorithms will be involved.
Large sky area multi-object spectroscopic telescope(LAMOST) is a reflecting schmidt telescope, the unique
telescope structure make it compatible with both large sky area and large aperture. While the vignetting effect
of the telescope is not the same everywhere, the flat field is quite different from the common flat field which use a
lamp projecting to a fixed white screen. We describe the Schmidt reflector(MA) cover solution of the LAMOST
flat field, simulation shows the variation across the field of view is less than 2 percent. The material of flat field
screen is carefully chosen to have both high reflectivity and diffusion. We also describe the material test for the
LAMOST flat field screen. Flat field lamp should have high color temperature to raise the sinal in the shorter
wavelength. The possible solution for the flat field lamp is described.
Atmospheric dispersion and differential refraction will lead to a non-neglectable light loss varying with wavelength across the field of view during the integral time of multi-fiber spectral observation.
These effects will be more severe in telescopes with large field of view such as the Large sky Area Multi-Object Fiber Spectroscopic Telescope(LAMOST). We have calculated the light loss due to atmospheric refraction for LAMOST. To improve the efficiency, we could move individual fiber to correct its 5000 A monochromatic displacement during observation, the best number of this kind of track should be balanced between the displacement correction and the fiber positioner error. We have calculated the best track number by
monte-carlo simulation for different declination field and different position of the field. Also we have derived the fiber positioner error tolerance from simulation.