Set Version 2
The MeasurementSet, Version 2.0
Athol Kemball - NRAO/Socorro
In AIPS++, observed data from both interferometers and single-dish
telescopes are stored in a common data format, referred to as a
Measurement Set (MS). The data format is designed to allow data to be
recorded in a generic format that is not instrument-specific, but
extensible to include local data required for individual
instruments. The MS format is an important counterpart to the generic
calibration formalism, known as the Measurement Equation (Hamaker,
Bregman and Sault 1996; A&AS 137, 117), which underpins calibration
and imaging in AIPS++, and is similarly designed to be
Measurement Sets in AIPS++ are implemented as AIPS++ Tables, and are
fully visible to scientific users of the package using the table and
tablebrowser tools. Additional tools such as ms and visplot allow
higher-level access to the data stored in an MS.
For the past several years, AIPS++ has used MS version 1, as defined
in AIPS++ Note 191.
This format has served the project well, but over
time needed to be extended to provide additional scientific
features. The discussion of possible revisions to the MS v1 format
took place within the AIPS++ project as a whole, and included
significant contributions from throughout the project. The resulting
MS v2 format was formally adopted by the project at the end of this
process, and is defined in
AIPS++ Note 229.
This is the MS data format expected by AIPS++ applications from
release v1.5 (November 2000) onwards. A conversion tool,
ms1toms2 has been provided to allow conversion of existing MSv1
datasets. These can also be filled from FITS or other data formats
into MSv2 directly.
The highlights of the new data format include:
- Closer integration of single-dish and interferometer data, including
support for generalized back-end devices, loads and reference
signals, and scheduling heuristics.
- Optional support for both lag-spectra and triple-product data in the
- Expanded VLBI support, including correlator models and frames,
pulsar gating, frequency groups and space VLBI.
- A more generalized flagging model, allowing both command- and
- Infrastructure to allow diverse observations and sub-arrays to be
- Separation of antenna pointing, source position and field center,
and polynomial representation of these positions for near-field or
- Expanded representation of history data.
- Generalized representation of Doppler tracking, covering single-dish
and interferometry Doppler tracking modes.
- Additions to the system calibration and weather tables.
- Expanded representation of polarization and frequency information.
Set Version II
The AIPS++ Data Repository
Darrell Schiebel - NRAO/Charlottesville
Release 1.4 will be the first release to contain the new AIPS++ data repository.
This repository was developed to move the data elements out of the source tree.
By moving the data which change slowly out of the source tree, the
download time for each AIPS++ build is lessened, and larger data sets can be
used and distributed.
CVSup was chosen
for use with the data repository for several reasons:
As part or the installation process for release 1.4, the repository specification
file will be set up to allow the user to update the repository. The way the update
happens is that new data files are generated in Socorro based on updates from the
data source, e.g. US Naval Observatory for
earth orientation information. These updates are then made available for AIPS++
users. The user can then choose when to synchronize with the Socorro data
- it does rsync updates of large
binary files, which allows only the modified tail-end of binary files
to be shipped and then patched onto the existing older version of the
- it has optimizations for dealing with RCS and
CVS repositories which permit it
to minimize traffic.
- it is used by FreeBSD so it has
a large body of users who maintain it and ensure that any security
problems are handled.
- once the specification file is created, it is easy for users to keep
the data repository up to date and to monitor the updates as they
happen (we plan to include CVSup binaries with the release).
The repository is divided into sections based on content:
The sections of the repository which are likely to be of most interest to end users
are the source and spectral line catalogs (these are generally not in place
yet) and the demo section which will contain test data and data used
as part of AIPS++ demos and examples.
- individual institutions, e.g. NRAO, BIMA, etc.
Our goal is to continue to expand the repository and in time to allow users to
choose which pieces they wish to keep locally and synchronized, and which pieces
should be accessed on-demand. One of the next things we plan to add shortly is the
Poynter and Pickett Submillimeter, Millimeter,
and Microwave Spectral Line Catalogue. This and other catalogs should make
the repository useful not only for internal AIPS++ applications, but also for direct
use by end users.