Queued Service Observing
General principles of Phase 2 (PH2)
Abstract -- This document presents the generalities of the Phase
2 tool (PH2) and the basic concepts of QSO observations
preparation. This document is not instrument-specific and applies to
MegaPrime, WIRCam, and ESPaDOnS.
Keywords -- Purpose of PH2, Technical notes, PH2 interface,
the concept of Observations Groups made of IC/C/OB, PI-defined
calibrations, Summary, Contact information.
Purpose of PH2
PH2 is a web-based tool that allows PIs of
accepted QSO proposals to prepare a full description of their
observations. This description is stored in a database, which is used to
prepare queues of possible observations. PIs can tell the QSO Team what
to observe, how, and sometimes even when.
- PH2 is compatible with Netscape, Internet Explorer, and Firefox
browsers. We highly recommend the Firefox browsers. Due to the recent
prolific development of browsers on several platforms, we cannot support
all of them. Browsers on Unix, Linux and Windows platforms are usually
the most reliable for working with PH2. PH2 now works also with the
Safari version 3 browsers.
- Except for one optional tool, PH2 does not include any
- Some of the information entered during Phase 1 (Title, Abstract,
contact information, target coordinates) is automatically transferred to
- Target information can be entered quickly in PH2 by uploading a
specifically formatted ASCII file.
- There is a time-out of 2 hour for inactivity periods (that is,
between "save" activations). A window reminds the user of this 2
minutes before the expiration of the session. Save your work frequently!
If you cannot access PH2 due to this but immediately must do so, send
us an email and we will correct the situation.
- To ensure data integrity, only one session with the same user ID is
allowed at a time.
- During the Phase 2 period, you can access PH2 at all time and as
many times as you want. All your work is saved in the database so you do
not have to finish everything at once... Also, there is no "submit"
button: when you're satisfied with the preparation of your observations
(for instance, what you see in your program summary), that's all there
is to it!
- PH2 allows the observations of moving targets (e.g. Solar System
objects) by entering targets
ephemeris. Starting with semester 2009A, PH2 also offers non-sidereal
tracking; non-sidereal guiding is not offered, for any of the
instruments. Due to the telescope's limitations, tracking without
guiding is only good for less than about 2-3 minutes. If you select the
tracking option, please keep your individual exposures under that
length. Programs with moving targets can be complex so do not hesitate
to contact us during the preparation of your observations.
- It is possible to define "user dithering patterns" for the imagers in
PH2. However, this practice is not recommended because it can result
in severe difficulties during the data reduction. Only use the
nonstandard dithering patterns when necessary, or if you are already
very familiar with data analysis.
- Due to some difficulties in tracking the sizing activity applied
to a browser window from PH2, we recommend that
you size PH2 to the maximum allowed by your screen at the beginning
of the session (before logging in) and keep it that way. All the
necessary scroll bars have been implemented for navigating within the
The typical PH2 interface is shown below:
You can change the size of all the frames inside PH2 by dragging
their side with the mouse.
- Navigation Menu: The left frame is a navigation menu,
with buttons for the different sections of PH2. The button corresponding
to the current section goes from blue to white. Quick Help Files and a
Tutorial are available from the bottom buttons.
- Top Frame: If present, it either displays non-editable
content (e.g. list of target names) or selectable options.
- Middle Frame: This frame presents the tables for the
targets, instrument configurations, constraints, etc. The maximum number of
rows displayed at once is 5, but buttons allow the user to navigate
through different pages inside this frame. At the bottom of each table,
a series of buttons allow the addition, duplication, deletion, or
selection of rows. The purpose of each button is explained by placing the
mouse over them.
- Bottom Frame: This frame includes the buttons for saving
the data to the database, cancelling changes, and a help button. Placing
the mouse over each
button makes a short description appear. When the
"Save" or "Proceed" buttons are pressed, the information is
automatically saved in the database.
The concept of Observation Groups -- Observation Groups (OGs)
are the entities selected from the database, put in the queues, and
executed at the telescope by the Service Observer. This subsection
explains which entities make an OG.
The entire architecture of PH2 and its database is based on the
concept of Observation Blocks (OB); each OB is made of one (and
only one) target, one (or many) instrumental configurations,
and one (and only one) set of constraints. Each target, configuration or
constraint is a unique entity and has a unique label. A target,
configuration, and set of constraints may be used more than once, to
define various OBs and OGs. Since it is easier to schedule short
observations at the telescope, there is a limit of 2 hours (7200
seconds) for the total integration time of one individual observation
- Targets can have fixed coordinates (Fixed Targets, or FT), or
coordinates defined by ephemeris (Ephemeris Targets, or ET). For each
instrument, tools are available to bring up finding charts and refine
the pointing or the identification of the target.
- An Instrument Configuration (IC) consists of a filter, exposure time,
and dithering pattern (for an imager), or an observing mode, exposure
time, and Stokes parameter (for ESPaDOnS). An IC can be used in more
than one OB and OG, so there is no need to duplicate identical ICs.
- Constraints concern the desired Image Quality, sky background level,
and airmass range. A set of constraints can be used more than once, so
there is no need to duplicate identical sets.
An OB is simply created by picking one target, one or more ICs (for
example, an IC for a red filter plus an IC for a blue filter; or the IC
for Stokes Q and the IC for Stokes U), and one set of constraints.
To add more flexibility to PH2, the concept of Observation Groups
(OG) has been introduced. The interface to prepare the groups is
illustrated below. Three different types of OGs are available, as
- Single OB (1OB): One OG is made up of 1 OB. If all OGs are
of this type, they can all be created quickly by using the button "Quick
Create OG" button.
- Sequence (SOB): It is possible to create a
sequence of OBs, and link different OBs (or the same OB!) that should be
successively, under the same constraint. An SOB can include different
targets, but due to the additional overheads introduced, this is not
recommended unless necessary.
- Monitoring (MOB): If an OB must be observed several times
with a regular period, a monitoring OG including this OB can be
defined, using a period, a number of iterations, and a minimum number of
Each OG can have a comment, which will appear when the database is
queried. These comments are extremely helpful, and can include
specific additional constraints or repeat information found elsewhere in
PH2 (e.g.: "Observe at -1hr < HA < +1hr"; "<0.3mag extinction for this
target", "Follow with OG34"; "Double star, pick faint one"; "Observe May
As each OG is created, the remaining I-time is calculated. If you
exceed your allocated I-time, you will not be able to save your latest
PIs are not allowed to define
detrend calibrations, for any instrument (biases, darks, any type of
flat, comparison exposures). For the imagers, PIs do not need to define
photometric calibrations using standard stars for the broad-band
filters; this is taken care of by the QSO Team. PIs must define
narrow-band calibrations if they need photometric calibrations. ESPaDOnS
PIs must define, if needed, spectrophotometric, polarimetric, telluric,
or radial velocity calibration stars and observations.
A summary of what has been entered so far for a
program is available under "Summary". This summary can be emailed to any
number of recipients by entering email addresses in the box found at the
PIs may contact the QSO Team at any
time by email, by using qsoteam -=at=- cfht.hawaii.edu