# Presentation: 912815

## A large array of telescopes in Antarctica with all-sky imaging every 5-10 seconds

- eXtreme Imaging Antarctic Network (XIAN)

- Don York, University of Chicago
- Great Surveys
- Nov. 20, 2008

## China

- D.York (Chicago),** **X. Cui (NAIOT),  L. Wang (Texas A&M),
-  C. Pennypacker (SSL)
-  X. Yuan (NAIOT), X.  Zhou (CAS, Beijing), Jingyao Hu (CAS, Beijing), Wen-Ping Chen (NCU, Taiwan), L. Feng (PMO, Nanjing), Z. Jiang (NAOC), Z. Shang (Tianjing Normal Univ.), J. Yang (PMO, Nanjing), J. Yan (PMO, Nanjing), Z. Zhu (PMO, Nanjing),)
-  Australia
- J. Storey (UNSW), M. Ashley
- (UNSW), J. Lawrence (UNSW), D. Luong-Van
- Europe
- E. Cappellaro (INAF, Padova), R. Malina (LAM, France),), S. Basa (LAM, France)
-  USA
- M. Blouke (Ball Aerospace), D. Lamb (Chicago),
- D. Harper (Chicago), R. Kessler (Chicago), D. Sandford (Chicago), J. Thorburn (Chicago)
- Science Case Assistance
- H.-W. Chen (Chicago), A. Puckett (Chicago),
- S. Hawley (U. Washington), B. Wilhite (Illinois)

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-   50-cm Schmidt telescopes (Br. Band, 5000A)
-   4000-8000 sq. degrees of sky
- 	(20 sq.deg. x 400)
-   Full sky image every 5-10 sec
-  1 arcsec pixels, 2 arcsec images (16K x 16K)
-   Mag. Limit: 20 V in 10 sec, 23 V in 1 hr.,
- 	25 V in 1 day (using co-addition)
-  No moving parts
- Dewars, for lab and summer testing
-  Automatic transient detection, trigger of BT (10-60 sec)
-  Automatic false positive rejection
-   Option of filters and/or polaroids, later.

- Key features:

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## Science Goals--Time Domain

- Physics of supernovae
-    --Orphan afterglows (GRB opening angle)
-    --Type II blue flash, early time Type Ia curves
-    --Type II counts at low z
-    --GRB physics (spectra, ISM)
-    --GRBs, cosmic distance scale (-ray, X-ray)
-    --Calibration of gravitational wave events and    		neutrino bursts
- Cosmology [, Ho, distance as f(z)]
- Planets --gravitational lens, eclipse searches
- Stars (pulsation, flares, CVs, eclipses)
- Deep optical survey (much deeper than SDSS)
- Ultimately, different filters plus polarization

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## Slide 5

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## The Need for Xian

-  Once the flash is detected, FOLLOW-UP is currently intermittent, owing to
-      --the impossibility of getting complete light       	curves (hence, of defining phenomena)
-      --lack of acceptable weather (NOW!) at a 	properly equipped site (spec, colors. pol.)
-      --lack of a system to allow overriding  of 	on-	going programs (VLT is exception)
- --lack of a system into which ALL new 		optical/IR followup is reported (NOW!)

- .

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## The Need for Xian

-  Therefore, the light curves are not well known
-  As more objects are added when one has small numbers,
-    the characteristics of a class are more fully defined
-      --Some objects die out and recover
- 	(but, usually no follow-up)

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## The Need for Xian

- --For the last fourteen years, it was not realized that short bursts (< 2 sec bursts) had a long tail with the same amount of energy in it as the short spike.
- --Physics of events
-    (short bursts=merging, condensed matter stars;
-    long bursts =collapsing stars-SNe II) is more
-    complicated than thought: event categories
-    overlap (now that more redshifts are becoming
-    available)

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## The Need for Xian

- As in every field of astronomy, one needs complete survey/classification
-      stage to get the right answer
- Serendipity (many time scales
-      unexplored)

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## Contour map of Antarctica

- USGS image

- Mount Kosciusko: 2,228 m

- Dome C

- South Pole

- Dome A

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## 6 am

- Galactic center

- South Celestial Pole

- June 21st
- Equatorial coordinates

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## Galactic center

- 12 pm

- 12 am

- June 21st
- Equatorial coordinates

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## 6 pm

- Galactic center

- June 21st
- Equatorial coordinates

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## Galactic center

- 12 am

- 12 pm

- June 21st
- Equatorial coordinates

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## Evaluation of performance

- = the number of objects expected in one year (objects/ sq. deg. - yr)

- h = total no. of square degrees scanned by a given survey project in one year, at some integration time.

- Number of objects sampled=  x h

- h (typical)= 0.33    x    0.5    x   x    N    x  xx   

- Efficiency of finding (software)

- Number of fields covered in the **timescale** being searched

- Dark moon

- Dark hours

- Telescope FOV

- weather

- seeing

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## Example evaluations

| Time-scale | Project | Day/nt.x moon | x N | x | h(sq.dg.-yrs.) |
| --- | --- | --- | --- | --- | --- |
| 2 day | SDSS-SNe | 0.33 x
0.5 | 7 x 43 | 0.8 x 0.6 x 1 | 24 |
| 60s | SDSS-I | 0.33 x 0.5 | 0.7 x 1 | 0.8 x 0.6 x 0.2 | 0.01 |
| < 1000s | SWIFT
 ray | 1 x 1 | 104  x 1 | 0.8 x 1  x 1 | 8000 |
| 10s to
3 mo. | XIAN | 0.33 x 1
        (?) | 20 x 400 | 0.8 x 1 x  1 | 2112 |

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## Occurrence rate for short transients (=0.01/ deg.sq.-yr==>1/day)

|  | (sec)                                 V lim            #/yr.                    Reference |  |  |  |  |
| --- | --- | --- | --- | --- | --- |
| GRB | 2-200 | 0.02 | ------ | (44) | Fenimore 1993 |
| GRB AG | 200-1000 | 0.01 | 14-23 | 22 | Lamb et al. 2006 |
| Orphan AG | 103-105 | >2 | 23 | >4400 | Zou et al. 2007
Gal-Yam 2005 |
| Blue flash | 600 | 0.04 | 21.5 (z=0.1) | 88 | Blinnikov 1998
Mannuci et al. |
| AM CVn | 600 | 10-3 | 19 | 2 | Anderson 2005 |
| Planet  eclipses | 3600 | 0.01 | 13 | 22 | ( coming) |
| Planet lenses | 1000 | 0.01 | 19 | 22 | Beaulieu 2006 |
| QSO /SN lenses (Ho) | 104-105 | 0.01 | 22 | 22 | Bolton,Burles
2003 |

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##   Occurrence rate for long transients

- =0.01/ sq. degree-yr.  means ~1 per day over entire sky)
- GRB)=0.02)

| 1 hr. resol.
for | mag. limit | 
 | #/year |
| --- | --- | --- | --- |
| Type Ia SNe | 23 (z=0.3) | 4.4 | 8800 |
| Type Ib/c SNe | 23 (z=0.3) | 0.02 | 40 |
| Type II SNe | 23(z=0.1) | 0.2 | 400 |
| AGN | 21 | 100 | 200,000 |

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## Figures of Merit

|  | 30s | 60s | 1000s | 106s |
| --- | --- | --- | --- | --- |
| of the sky | -------- | --------- | 600/ 12 | --------- |
| ROTSE | ------- | -------- | 1.7/ 18 | -------- |
| SDSS SNe | -------- | [0.01/ 22] | --------- | 24/ 22 |
| T2-APO | 1.2/ 20 | 1.2/ 21 | 1.2/ 23 | 72/ 23 |
| LSST | [0.6/ 26] | [0.4/ 26] | [0.01/ 29] | 2240/26 |
| XIAN | 2112/ 20 | 2112/ 21 | 2112/ 23 | 2112/ 25 |
| [....]=> | If fully | dedicated | in this  | mode. |

- h (sq.deg.-yr.) / limiting V mag for 4 integration times

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## Occurrence rate of FALSE POSITIVES that   

- must be removed in real time, uniquely
- removable in real time with Xian

|     TYPE | TIME-SCALE |  | MAG.
LIMIT |   Notes |
| --- | --- | --- | --- | --- |
| Cataclys.
variables | 1000s | 1
 | 19 | Szkody,
ROTSE |
| Red dwarf
stars | 1000s | 1
 | 23 | Kulkarni
And Rau |
| Asteroids
 | -------- | 103 (Rotse)
106(SDSS) |   17.5 mag
22  mag |  |
| Backgr.
radiation | ------------ | 108
 | < 20 | 1 /cm2/sec
assumed |

-                                Compare =0.02 for GRBs.

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##  Avoid false positives

- --variable detector artifacts (too slow to matter)
- --solar system, atmospheric events (high proper motion, streaks, pattern)
- --saturated stars (mask)
- --stars that make “dipoles” because of variable PSFs when comparing frames (track image size with repeating stars in each part of sky)

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##  Avoid false positives

- -- radiation hits (cosmic rays or gamma
-    rays from equipment near the CCDs)
-   (will not repeat)
- --ghosts from Schmidt systems (which
-   move as strip scans) (need AR coatings)
-  (predict)
- --true variable sources, cataclysmics, red
-   dwarf flares  (1 day template, 25th mag)
- --slow moving asteroids (track as they
-    enter big field)

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## Triggers for Transients

-   Compare successive drift scan segments, line by line.
-     (example, 150 lines per segment, up to 70 readouts per 8000 line
-     CCD)
-   Co-add in, e.g., 100s, 3000s, 10 hr, 100hr., 1000 hr., images to look
-    for triggers for longer time scales (orphan afterglows, SN Ia or
-    AGNs). Full reductions (photometric and astrometric) for these.

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## Slide 24

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## Slide 25

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## Slide 26

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## PANDA-2007, 2008 (China lead-Polar Research Institute of China)

- Power from PLATO-jet fuel, 1.5 KW
- Disks, instruments separate
- Site testing:
-     --surface layer turbulence boundary
-     --sky background, cloud cover
-     --sub mm transparency
-     --C-Star (four 14cm Schmidts, Pole)
-     --Various problems in most cases, retrofits now on the boat for new traverse and another year.

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## Slide 28

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## Conclusions

-   Xian will impact the study of GRBs, cosmology, supernova physics,
-    planets, variable stars, gravitational waves and neutrino astronomy
-  In time domain discovery (< 2 day events), Xian is >1000 x better
-     than anything yet built or planned.
-  The 16Kx 16K CCDs are feasible to build. Low power electronics is
-     a major development.
-   The minimum-moving-parts goal is attainable
-   There are previous experiences to build on, but a large step is needed
-   Fast algorithms will be a major (not insurmountable) challenge
-   CSTAR, T2, T3are logical first steps
-   Xian on the Antarctic Plateau is feasible and should be built

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## Acknowledgements

- While our designs developed independently, many of the ideas here were also arrived at, in connection with the TOMBO*  project, by Y. Ohno, T. Ebisuzaki, K. Sunouchi, R. Susukita, C. Otani, H. M. Shimizu, A. Yoshida, No. Kawai, M. Matsuoka, M. Euno, T. Wada, M. Yamauchi and N. Takeyama, Riken Review No. 47, July 2002. We acknowledge discussions with C. Akerlof.

- *TOMBO stands for Tombo Observing for Microlensing and Bursting Objects.

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## Schmidt Layout (single corrector) 01.14.07

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## Desiderata

- 0.5 meter Schmidt
- 1 arcsec per pixel (9 micron pixel)
- 80% encircled energy in 1 pixel (ADC)
- 3860A to 9000A
- 26% obscuration
- f/3.28
- Focus independent of temperature

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## Off axis: 0, 0.5, 1.0, 1.5, 2.0 and 2.5 degrees. Bar at upper left is two pixels, 2 arcsec.

- SPOT DIAGRAMS

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## CCD Design (example)

- QE > 50% (red favored?)
- Read noise < 2 electrons, rms (on chip,
-    variable gain)
- Integration time 22s, drift scan
-   (10s with more readouts)
- Pixel size 9-10 microns
- Well capacity <0.99995 electrons
- Dark current < 0.1 electrons per sec
- Serial registers per unit: up to 8 to 13
- 1 TDI unit: 2000 x 8000 pixels
- 8 preamps per unit, 250 lines per read
- 8 + 8 units per focal plane
- 16K x 16K pixels
- Power dissipation per focal plane 16W

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## TDI CCD Layout (1/2 focal plane)

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## Data (per telescope)

- --52 megabtyes/sec for the triggers
- --2 Terabytes per night, short term storage
- --4 Terabytes long term storage (will increase as storage becomes cheaper)

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## Slide 19

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## KS-Technical Desiderata-1

**Maximum coverage at Dome C/A**
**     ****--Circumpolar sky is large, excellent**
**	****	****observing efficiency, cold**
**No moving parts: natural focus, one filter,   **
**        ****no telescope motion, no(?) CCD Dewars**
** ****Trade off CCD block size design (t ****min****) with acceptable yield on amplifiers**
**Single pixel triggers, drift scan**
**Magnitude limit in selected time**
**Low power because fuel is expensive**

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## KS-Technical Desiderata-2

**Minimize computing goals, evolve as technology evolves**
**   ****-- t(short) to t(short) comparisons**
**   ****-- Send triggers to separate pipeline for  **
**      ****evaluation, pull out that track of triggered **
**      ****object to get long  timescale information**
**   ****-- Co add and compare for longer time scales**
**   ****-- Discard most frames after co-add’s are  **
**      ****done (consider look-back requirements)**

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## KS-Technical Desiderata-3

- Follow-up maximal number of selected classes of bursts with on-site, conventional, well equipped telescope, sized to science:
-      --spectra, IR, optical (for redshifts to 10)
-      --photometry (optical, IR)
-      --polarimetry
-      --autoalert, fast tracking
-  This is called BT.

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## KS-Technical Desiderata-4

- Expect to learn with time about triggering strategies.
- Build small array for tests of engineering, fabrication, trigger rates, false positives

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## T2,T3, T5

-  10-100 sq. deg. (2-5 telescopes, underfill focal plane
-         with CCDs if need be.)
-  Self-reliant science goals (does not depend on KS):
-       --Minimum set of orphan afterglows
-       --Minimum set of blue bursts, SN II
-       --Confirmation of SN II /SN Ia rate at low z
-          (z~0.3).
-       --Deep co-added survey (SDSS imaging
-           equivalent)

- T2,T3, T5

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## T2,T3, T5 -Engineering

-     --software for triggers (identify sources of
-       false positives)
-     --test triggering schemes (different filters
-       each year)
-     --recognition of triggers early enough to get
-       correct follow-up (spectra, photometry)
-     --Dewarless CCDs, focus by design

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