The Observations of LAMOST

Jianrong Shi

NAOC

1/7 2014

The Observation of LAMOST

Jianrong Shi(NAOC)

OverviewThe structure of LAMOST

The observation preparation

How to select the plate

The results from one year Pilot and two year standard surveys

Structure of LAMOST

MB mirror

6.67 m×6.05m

4000 Fiber Positioning 4000

Fibers

MA mirror

5.72m×4.4m

16 Spectrographs32 CCDs

Characteristics of LAMOST A horizontal meridian reflecting Schmidt telescope with an

active correcting plate

large field of view (5 deg) + large aperture (4m) Active optics on thin-mirror & segmented mirrors

4000 optical fibers on focal surface Parallel controllable fiber positioning

The observation preparationFocus the MB ( Shack-Hartman MA) ~5mintues

Focus the MA and four guiding stars (center star V < 8 mag. ) ~25mintues

Moving the fibers to the accurate positions (9mintues)(Which can be done during the focus)

MB 6.67m×6.05m Focal length 20m 37sub-mirrors

8

Segmented Active optics for 37 sub-mirrors of MB

MA 5.72 m×4.4m (24 sub-mirrors)

10

Segmented and thin mirror active optics for 24 sub-mirrors of MA

11

4000 fiber positioning units (1.75m)GuidingCCDs

S-H sensorfor MA

4000 fiber positioning units

The site conditions

The statistics of the number of hours of BATC observations per night from 2004-01-01 to 2007-09-30. The dashed line shows the theoretical available time.

Sky brightness

The sky brightness in V band obtained from BATC Polaris monitor data, as a function of time from 1995 to 2011.

Telescope

Seeing: 3-5 arcsec (dome + site)Site seeing: < 2 arcsec ; Fiber size: 3.3 arcsechas a field of view as large as 20 square degrees, the effective aperture varies from 3.6 to 4.9 meters in diameter (depending on the pointing). Enables it to take 4000 spectra in a single exposure at resolution R = 1800.

Declination -10o 60o 90o

Effective aperture 4.9m 4.2m 3.6m

Field of view 5 degree 3 degree

Seeing

Comparing the seeing from guide star and DIMM during Pilot Survey (Oct. 24, 2011- Match 30, 2012 )

Throughpot (Oct. 1 2011)

Signal to Noise Ratio

Signal to Noise Ratio

Signal to Noise Ratio

Signal to Noise Ratio

Signal to Noise Ratio

Throughpot (Oct. 1 2011)

Throughpot (Oct. 2 2011)

How to select the PlateObservational conditions: (240m)weather, Moon phase, left time and seeing etc. VB(9.0<r<14.0) 3*10mB (14.0<r<16.3) 3*20m – 3*25mM(16.3<r<17.8) 3*30mF(17.8<r<18.5) 3*30mreadout ~ 8m Wish to observe two B plates and more VB plates

the image

The results from pilot surveySpectra with S/N>10（ g or i band） spectra plate success ratiopilot: 597,032 397 45.6%First year: 1,191,414 768 57.9%Second year:1,207,119 697 64%success ratio: the ratio of the Spectra with S/N>10

to all the selected targetsObserved time: 914h, 1278h and 1356h

The reason for the less plates during the second year

Increase the time for foucs MB、 B plate from 20 -25 minutes, added one lamp observation and more M plates observed LSS-GAC DR1 B： 76 M： 30 F： 4 DR2 B： 75 M： 44The instrumental fail rate (The ratio of the lost time due to the instrumental problem to the observation time)Pilot: 12.5% first： 5.3% second： 4.4%

Thank You！