Objectives - IRAM

The VLT Dataflow
System
Joseph Schwarz
European Southern Observatory

ALMA Project
The Egg Diagram
J. Schwarz - 13 January 2000 ALMA SSR - The VLT Experience

ALMA Project
Observation Blocks (OBs)
Central unifying concept
Include 1 target and n exposures
Built up from ‘templates’ (an ISO concept)
– Templates should cover ~90% of observations
Prepared by observer during Phase II
OBs intended to be atomic
OBs are what gets scheduled
J. Schwarz - 13 January 2000 ALMA SSR - The VLT Experience

ALMA Project
OBs are not ASCII files
OBs in Practice
– Can edit ASCII version, convert to OB format
There is no automatic tool for checking OB
correctness (except for syntax)
– User can ask for non-existent filters, 6 hr
exposure, or long acquisition image (even
though proposal was for spectroscopy only)
– OBs are currently checked manually
J. Schwarz - 13 January 2000 ALMA SSR - The VLT Experience

ALMA Project
OBs in Practice (cont’d)
OBs are often broken on the mountain
– When exposure m of n fails, ops want to avoid
repeating the target acquisition
– Conditions may change during OB execution;
do we want to throw out the good exposures
and wait ‘till we can do them all at once?
– Breaks the DFS to VCS interface
J. Schwarz - 13 January 2000 ALMA SSR - The VLT Experience

ALMA Project
An OB Example
Example consisting of 4 ASCII files
– .obx file: master w/acquisition template:
ISAACSW_img_acg_Preset + parameters
– .csx file: constraint set
– .tpx file: target information
– .odx file: observation description
uses template ISAACSW_img_obs_AutoJitter
– plus parameters
J. Schwarz - 13 January 2000 ALMA SSR - The VLT Experience

ALMA Project
Alvin_J-epoch1.obx:
name "Alvin_J-epoch1"
userComments "1. epoch observation of this SN"
userPriority "1"
calibrationReq ""
type "O"
template "ISAACSW_img_acq_Preset"; # type:
acquisition
DET.DIT "30"
DET.NDIT "4"
DET.MODE.NAME "DoubleCorr"
DET.WIN.NX "1024"
DET.WIN.NY "1024"
DET.WIN.STARTX "1"
DET.WIN.STARTY "1"
INS.MODE "SWI1"
INS.FILT1.ID "J"
INS.FILT2.ID "open"
TEL.TARG.ADDVELALPHA "0."
TEL.TARG.ADDVELDELTA "0."
TEL.ROT.OFFANGLE "0."
constraintSet "faint_SNe.csx"
targetPackage "Alvin.tpx"
observationDescription "SN_44m_J.odx"
J. Schwarz - 13 January 2000 ALMA SSR - The VLT Experience

ALMA Project
Scheduling
Long-term: follows OPC decisions
– Six-month observing period
– Allocates only VM nights & technical time
The rest is Service Mode
– Currently done manually
Six weeks for VLT + 5 La Silla telescopes
– Automated tool has been tested (see next slide)
J. Schwarz - 13 January 2000 ALMA SSR - The VLT Experience

ALMA Project
LTS: Trial Run
The LTS was used for Period 64 on 2 telescopes out of 7
Iterative Scheduling Process: You can never satisfy
completely all the Astronomers’ Requirements.
– Identify proposal constraints that cannot be respected
– Edit these constraints
– Run the scheduling algorithm
Results: needed 2 days to complete the Schedule of 2
telescopes, most time was spent analyzing the Proposals in
order to change the constraints in a proper way.
J. Schwarz - 13 January 2000 ALMA SSR - The VLT Experience

ALMA Project
Medium Term Scheduling
Done every month in Garching
– Database: list of certified OBs
– Reports: 1 per instrument
Bad seeing list
Bad transparency list
Very few accepted proposals want bad seeing…
J. Schwarz - 13 January 2000 ALMA SSR - The VLT Experience

ALMA Project
Scheduling (cont’d)
What the mountain does w/MTS is
instrument-dependent
– Ex: FORS team wants lots of subqueues
– OBs are selected and scheduled by hand
Short-Term Scheduler (STS)
– Based on HST’s Spike inference engine
– Different Scheduling Strategies to optimize the
different Objectives
J. Schwarz - 13 January 2000 ALMA SSR - The VLT Experience

ALMA Project
Objectives
Short Term Scheduler
maximize telescope utilization, minimize instrument
setup time, minimize the airmass, give greater
preference to Observations with higher scientific
priority
Constraints
target viewing, moon-target distance, moon phase, sky
transparency and seeing, timing constraints, instrument
configuration
J. Schwarz - 13 January 2000 ALMA SSR - The VLT Experience

ALMA Project
STS: Timeline Widget
Detail of the Timeline Widget which shows in a
graphical way the constraints of the selected
Observation Block
J. Schwarz - 13 January 2000 ALMA SSR - The VLT Experience

ALMA Project
Short Term Scheduler
Tool about to be commissioned
Learning curve is obstacle to its use
– Ops team is understaffed
– Mountain vs. HQ issues, too
Spike engine is coded in Lisp
– Lisp programmers hard to find, harder to keep
– Conversion to C++ would be difficult ($$, t)
J. Schwarz - 13 January 2000 ALMA SSR - The VLT Experience

ALMA Project
Pipeline Processing
FITS files received from VLT Control Sys
QC group took over unverified S/W
– “Reduction recipes”
– Reduction engine
– Experience w/site, telescope & instrument
necessary to make the S/W work
Biggest issue: identifying data received &
what to do with it
J. Schwarz - 13 January 2000 ALMA SSR - The VLT Experience

ALMA Project
Pipelines: Status
Supported & unsupported instrument modes
– Not all modes offered to observers
– Even supported modes need astronomer vetting
– More automation possible
– But pipeline was never intended to do
everything (e.g., all 40+ FORS modes)
QC group can produce raw data for SM
observers w/in 48 hours in urgent cases
J. Schwarz - 13 January 2000 ALMA SSR - The VLT Experience

ALMA Project
Archiving
All raw data frames & engineering data
Only a handful of FITS keywords in DBMS
– Restricts search possibilities
User Support doesn’t have a good tool to
determine observing program status
J. Schwarz - 13 January 2000 ALMA SSR - The VLT Experience

ALMA Project
Lessons learned
Design the control system & the reduction
system together - know their interaction
Anticipate a lot of time to understand site,
telescope & instruments
– Feed this understanding back to the software
Don’t underestimate “us vs. them” factors
– Mountain vs. headquarters
– Real-time vs. data reduction s/w developers
J. Schwarz - 13 January 2000 ALMA SSR - The VLT Experience