Download PULSE@Parkes science and technology overview

PULSE@Parkes science and technology overview
George Hobbs
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The PULSE@Parkes project aims to allow high-school students to undertake
observations using the Parkes radio telescope that are scientifically valuable, have
educational value for the students and demonstrate some key technologies for remote
observing at Parkes and future radio telescopes. The PULSE@Parkes project is a
prototype project for much larger-scale projects in the future with new facilities such as
ASKAP and the SKA.
In this document we outline the science and technology case for the PULSE@Parkes
project and describe work required in order to achieve the PULSE@Parkes goals.
1.0 Main science goals
This project has been developed for four major scientific projects. For two (listed below)
the PULSE@Parkes observations simply add extra observations to existing pulsar timing
projects. For the final two projects PULSE@Parkes provide the majority of the
observations.
GLAST/AGILE timing: The GLAST and AGILE gamma-ray telescope missions aim to
study the pulsed gamma ray emission from a subset of the known pulsars. In order to
fold the observed gamma-ray photons at a pulsar’s rotational period it is necessary for
radio telescope observations to monitor the pulsar’s spin over periods of many years. A
collaboration including both Northern and Southern hemisphere radio telescopes now
exists in order to obtain the required pulsar timing models. For young, glitching pulsars
it is necessary to obtain as many observations as possible in order to track each pulsar’s
spin down. The PULSE@Parkes project observes ~10 pulsars that are also monitored for
the gamma-ray experiments. These observations will be added to the main-stream
experiment.
The Parkes Pulsar Timing Array (PPTA): The PPTA observes 20 millisecond pulsars
with the aims of 1) detecting and studying an isotropic gravitational wave background, 2)
forming a pulsar based time-scale and searching for irregularities in terrestrial time
standards and 3) improving the Solar System ephemeris. The PPTA observations require
large numbers of observations. The PULSE@Parkes project observes ~4 pulsars that are
part of the PPTA sample. The observation times available to the PULSE@Parkes project
are relatively short (typically 10-15 minutes, compared with 1 hour for main-stream
PPTA observations), but will be used for improving calibration techniques and
monitoring the millisecond pulsar spin-downs. The related ARCC student project (see
below) will undertake full-length observations of these pulsars.
Pulsar timing irregularities: The Jodrell Bank observatory has been monitoring many
hundreds of pulsars for up to 40 years. This data archive has recently shown many
unexpected (and unexplained) phenomena related to the pulsar spin-down. The timing
residuals for many pulsars show unexplained oscillatory motion. It is possible that this is
due to unmodelled planetary companions to the pulsar or to the neutron star undergoing
free precession. Unfortunately, the data quality achievable with the current observing
systems at Jodrell Bank means that it is challenging to distinguish between these two
models. PULSE@Parkes observations of a set of these pulsars, observable from the
Southern hemisphere, are fully calibrated and will be used to search for small scale pulse
shape variations that are correlated with the timing noise.
Long-term nulling pulsars: The Parkes multibeam pulsar survey discovered a set of
pulsars whose pulsed emission seems to “switch-off” for long periods of time. When
“on” these pulsars are bright and can be seen using short observations. When “off” these
pulsars are completely undetectable. Unfortunately, the lack of observing time on
existing telescopes implies that the statistics of this nulling phenomenon is hard to
determine. The PULSE@Parkes observations (particularly with the 12-m telescope; see
below) will provide many more observations of these unexplained pulsars. NOTE: Must
add these pulsars to our observing list.
2.0 The 64-m telescope
The PULSE@Parkes project has been developed for the Parkes 64-m telescope. We
expect to obtain about two hours per month for this project with extra observations being
obtained from time-to-time during unallocated director’s time and for calibration
observations. The choice of science projects requires regular observations separated by
many weeks (for instance, it is not useful to have four observations in four days and then
have a large gap of four months before the next observation). A minimum time between
observations is approximately 1 week and a maximum manageable gap would be
approximately 1 month.
The PULSE@Parkes observations to date have relied on the prototype ATNF digital
filterbank system. For the next observation session (in Feb) we will use the PDFB2
system (or the PDFB3 system if fully commissioned). On longer time-scales we expect
to use PDFB3 and/or APSR for the observations.
The data will be collected in a mode suitable for standard data-archiving and processing.
We plan to develop monitoring software for the PULSE@Parkes observations (see
below).
3.0 The 12-m telescope
A 12-m ASKAP antenna is currently being installed at the Parkes observatory. This dish
is a test-bed for a focal plane array. It is likely that this telescope will only be in use for
short periods whilst the engineers to carry out their tests. For the remainder of the time
we propose to use this telescope as part of the PULSE@Parkes project. Initially we
envisage using one element of the focal plane array and the PDFB1 prototype digital
filterbank system. The small size of the dish limits the number of scientific projects
available, but will be ideal for monitoring the Vela pulsar and the long-term nulling
pulsars. The data will be monitored by high-school students using a web-based interface
(see below). Such projects using a small telescope are extendable and will provide a
framework for further outreach work with the ASKAP antennas or with MOPRA.
4.0 Technology demonstration
The PULSE@Parkes project allows the ATNF to develop and test methods for remote
operations at the Parkes and ASKAP observatories. All observations will be carried out
remotely, but, for the foreseeable future, a member of the team will be in the Parkes
control room to monitor the observations and will be able to take control if necessary.
We are working with members of the ICT centre in order to develop a “remote
observation” room in which the students feel as if they are at the telescope. Such
techniques may subsequently be used for professional remote observations of the ATNF
telescopes.
5.0 Relationship with the ARCC projects
The Arecibo Remote Command Center (ARCC) is a similar project with the aim of
carrying out remote observations of pulsars using the Arecibo telescope. The ARCC1 is
based in Brownsville, Texas and the ARCC2 in Milwaukee. We plan to allow at least
two observing runs per year by the ARCC students. This will develop our overseas
remote operations capability and provide the opportunity for U.S.A. high school students
to access Australian telescopes. The ARCC students will also take part in main-stream
P456 (pulsar timing array) observations. These observations will use the tools set up for
the PULSE@Parkes project, but will not be officially part of the project. The time and
number of the P456 observations will be decided by the timing array collaboration.
6.0 Student experiments
Various student experiments will be developed over the coming years. The experiments
will be based on pulsar timing data taken by the students and using archived data
observed by previous school groups. When the PDFB3 search mode has been
commissioned (early 2008) we intend also to allow a few groups to record search mode
data of known pulsars (and blank sky). This will allow the students to carry out a
standard pulsar search in order to attempt to “discover” the pulsars. We will initially
concentrate on the following three experiments:
6.1 Measure a pulsar’s distance
For every pulsar observation the students will obtain a text file that contains the folded
pulsar profile for various different frequency bands. The students can subsequently use
EXCEL (or equivalent program) to measure the pulsar’s dispersion measure (DM) and
hence obtain an estimate of the pulsar’s distance. This project allows the students to 1)
analyse their observations, 2) study how pulse shapes vary across the observing
bandwidth, 3) determine the effects of interference, 4) understand the concept of
“dispersion”, 5) learn that pulsar’s are all at different distances, 6) measure the pulsar’s
distance in light years and 7) learn about equatorial and Galactic coordinate systems.
Each school group can, for a given pulsar, compare their measurement of the pulsar’s
DM and/or distance with previous groups and with the ATNF pulsar catalogue.
6.2 Measuring the age of a pulsar
In this project, the students compare the period of the pulsar measured for their
observation with previous observations. In most cases the pulsar will be spinning slower
and therefore the students can obtain an estimate of the pulsar’s slow-down rate and
hence its 1) characteristic age, 2) surface magnetic field strength and 3) energy loss rate.
In some cases the pulsar may seem to be spinning faster. In such cases, the pulsar will
have undergone a “glitch event” – an event of great interest to professional astronomers.
This project allows the students to 1) understand the importance of comparing their data
with previous data sets, 2) determine the “age” of an astrophysical object and can
consider whether this is the pulsar’s true age, 3) understand that pulsar’s magnetic fields
are extremely strong and 4) search for astrophysically interesting effects such as
“glitches”.
6.3 Searching for a pulsar
Using “search mode” observations the students will 1) de-disperse the signal, 2) Fourier
transform and 3) search for periodicities. If periodicities are discovered then the students
can “fold” the time series at the period of the candidate pulsar in order to view the
“folded pulse profile”. The students can select whether to observe a patch of blank sky
(in which case they may be lucky enough to discover a pulsar!) or to observe a known
pulsar (in which case they will be guaranteed to see the pulsar).
The students will learn 1) the basis of pulsar searching, 2) the basic concepts of Fourier
transforms and 3) may be able to discover a pulsar.
7.0 Work required
The scientific and technical aspects of the PULSE@Parkes project have been worked on
by G. Hobbs, D. Champion and M. Carr. The work undertaken so far has been to
develop systems quickly that can be used to test various aspects of the project. It is now
necessary to plan and produce the final versions of the 1) observing system, 2) data
monitoring, 3) data log, 4) data storage and archiving, 5) link between Epping and
Parkes, 6) web access and 7) software for pulsar searching and timing.
This work could be undertaken by existing group members (mainly G. Hobbs), but would
not be well designed, nor implemented. We should consider that a part-time position
(approx. 2 days per week for ~6 months) be made available where the successful
candidate will develop the hardware and software aspects of the project. The job will be
divided between work required at Parkes and at Epping.
7.1 Requirements for Parkes
1) Develop a straightforward manner to install web-cams and sound recording
systems at Parkes that can be removed/shut-down immediately after observing. It
should be possible to view the 1) control room, 2) outside web-cam and 3) aztrack web-cam.
2) Record the sound of the pulsars (or whatever the pulsar is observing) and stream
the sound to the Marsfield lecture theatre.
3) Allow the astronomer to talk/chat with the students in the Marsfield lecture
theatre and log the discussion.
4) Automate data collection, storage, processing and data transfer to Epping.
5) Provide automated monitoring software (web-based) enabling the students to
view the data (both from SPD and the DFB output)
7.2 Requirements for Epping
1) Liase with the ICT centre in order to provide an effective way for the students to
carry out remote observations
2) Develop and test a web-based archiving system allowing the students to view
their observations and related log-files.
3) Allow the students to keep a log of their observations
4) Develop software required for the student projects
5) Consider methods for allowing access of the remote observing system from sites
away from the ATNF (e.g. from schools)
7.3 General design
The data transfer between Parkes and Epping and data monitoring should be designed as
follows.
7.3.1 Observing
Observing is carried out using VNC (or equivalent) terminal at Epping running on Parkes
machines. The data will be recorded as normal at Parkes from the PDFB2 system. At a
future date it may be possible to produce web based observing software that will allow
the VNC link to be discarded.
7.3.2 Data monitoring and observing
A MySQL database at Epping will be used to store each observation. The database will
contain 1) observer information (student group name, date, school name …), 2) log
information (from log files produced by the student and/or astronomer for the specified
observation), 3) information about the observation (file name, pulsar name, instrument
used …) and 4) observation data (text files containing the pulse profile, sound files
containing the telescope output in sound format …). The raw archive will be stored as
normal as part of the standard pulsar observing database.
A web-based interface will be used to 1) monitor each observation, 2) fill the database
and 3) allow the students to produce a log file. This web-based interface will have a
check-list for each observation:
1. log-in: allow the students to type in their group name and select a pulsar
2. contact astronomer at Parkes – okay to observe?
3. start the observations using the VNC link (click okay when done)
4. monitor the observations by viewing the pulse profile updated every subintegration
5. keep a log file
6. click a button when finished observing (this then copies the files across and fills the
database and logs the group out of the system)
7.3.3 Data archiving
A web-based interface is available to access the MySQL database. The interface allows
students to search for their observations (or to obtain all observations of a given pulsar)
and to view the log files or to download the text files for subsequent processing.
8.0 Miscellaneous
These are general ideas that may, or may not, be of interest …
1. Have one session per year for a different non-school group (e.g. local astronomy
society, operations staff …)
2. Have four modes of operation: observing from Epping, observing from school,
observing overseas and no observations
3. Have future mode for transient/SETI searches
4. Only have one person at Parkes