1. Key Inputs / Requirements
Version 0.5
TLH
16-Mar-05

2. Science Galaxy Formation and Evolution
ISM, Disks, Star and Planet Forming Regions
CMB and the SZE
Solar System Studies
KBOs and Irregular Satellites
Write-ups are progressing
The unique science of CCAT will be enabled by
Combination of wavelength coverage, sensitivity, field-of-view
Sensitivity is influenced by confusion (aperture size is very important)

3. Top Level: Requirements
Item
Req’ment
Goal
Notes
Aperture
25 m
> 25 m
Sensitivity/Confusion
Wavelength range mm
200 – 1100
Field of view
10’
20’
Surveys
Pointing spectrographs cameras
0.35” 5” 2”
0.2” 3” 1”
@ 350 & 200 mm blind pointing reconstructed
Tracking one hour 20 min 10 sec
1” 0.25” 0.17”
0.5” 0.15” 0.1”
Spec-Photo req’mt
Elevation limits
From horizon
Azimuth Range
270
0 is north
What is reasonable time to move, repeak and move back on a source?
Dead time at zenith ~ 2*10deg*60arcmin/deg*4sec/arcmin = 4800 seconds

4. Top Level: Requirements
Item
Req’ment
Goal
Notes
Infrared mode (l < 40 mm, non-redundant masking)
< 5 mm rms TBD panels
< 5 mm rms 90% of panels
Circumstellar disks
Polarization capability (should be vs. l)
calibratible to 0.2%
calibratible to < 0.05 %
Star forming regions, still TBD
What is reasonable time to move, repeak and move back on a source?

5. Ancillary: Requirements
Item
Req’ment
Goal
Notes
Instrument location
Nasmyth
Ltd. bent Cass
Access, size, loading
Delivered instrument f#
f/8
f/6
Window/mirror sizes
Focus dist. (from flange)
1 m (TBD)
---
Nominal
Focus range
0.5 m (TBD)
1.0 m (TBD)
From nominal
Chopping Hz
0-1 Hz
With M2 and/or M3?
Scanning requirements
0.2 (/s) 0.14 (/s2) TBD ('')
(/s) TBD (/s2) TBD ('')
Rate (all directions) acceleration reconstructed pointing
Based on “first-look” at instruments. Need further work on instrument concepts.
Tech Memo on Chopping & scanning requirements being written by Dowell, Gowala, et. al.

6. Ancillary: Requirements
Item
Req’ment
Goal
Notes
Instrument mass
< 2 tons ?
per instrument
Instrument volume
TBD
Instrument power
< TBD kW
Online instruments
2 (TBD)
4 – 6 (TBD)
Programmatic, weather
Secondary blockage
< 4%
< 2%
Daytime ops
limited
24 hours
There should be a few “typical” instruments which define the envelope of power, mass, and volume.
Do we really need to have the “max” available for all online instruments?

7. Sensitivity Estimates: Status
The atmosphere
Data, models, & statistics in-hand & synthesized
Continuum detection of point sources
Herter, Stacey, Dowell, Bradford (basically agree)
Confusion limits provided by Blain
Low-Resolution spectroscopy
Need to check yet
Heterodyne
Need inputs on this

8. Atmospheric Transmission
1000
450
350
200
Pardo models for 5000m (Radford). Optimized bands shown.

9. Water Vapor Stats
From Blundell et. al (2002) tau(1.35 THz) statistics

10. Sensitivity vs. PWV
1-sigma in 1-second. Assume 30 deg from zenith, loss of for differencing, 12 mm rms surface

11. Performance vs. Surface rms

12. CCAT Instrumentation Bolometer Array Cameras – more than 10,000 pixels
350 and 450 m at first light
620 and 850 m, likely in same dewar – filter wheel?
200 m likely 3rd band
Direct Detection Spectrometers
R =1000, 16 x 128 short slit grating spectrometer
Spatial multiplexing
Resolving power well matched to extragalactic science
R = , Z-Spec like wave-mode coupled spectrometer
Coherent spectrometers for high spectral resolution science: e.g. Galactic star formation studies
Spatial multiplexing important for extended sources
Focus on shorter submm science, where we have a more distinct niche