Guest Observer Facilities
& Science
Centers
|
NASA Archives
|
|
About the HEASARC:
HEASARC Overview:
Motivation & Requirements >
Data Formats & Software
Motivation and Requirements
Motivations
There are four distinct categories of motivations for archiving high
energy astrophysics data: historical studies, theoretical follow-up, surveys
and assurance.
Historical studies are the most obvious archival activity. An
observer discovers a new phenomenon, or is studying one previously known,
and needs to check earlier data to independently confirm its existence and/or
track its long-term variability. These studies can be the most difficult type
of archival activity because they involve combining and/or comparing datasets
from different telescopes. The major issues to consider for historical studies
are ease of access to data, and the ability to perform cross-instrument
calibration. An activity related to historical studies is the use of archival
data as part of a justification to propose the use of a new telescope.
Theoretical follow-up is the need to test new models against existing
data. In many cases, the interpretation of a phenomenon can take many years,
with theoreticians repeatedly building models and testing them against the
data. Theoreticians previously had to work closely with the original
investigator to test their models, or they had to make "eye-ball" fits to
published data. The major issue for theoretical studies then is that the
theoretician does not have a detailed of the instrument characteristics or
analysis techniques. He or she simply wants a data product and the associated
calibration to test against the model in a clearly-described, easy-to-read data
format.
Surveys provide the opportunity to combine many observations of a
single class of object (e.g., AGN) made by many different investigators using
the same telescope and instrument. The current principal investigator approach
to allocating observation time means that large, uniform samples of particular
object types are rarely available to a single observer. Only after the data
enter the public domain can a survey of the properties of a particular class
of object be made. The main issue regarding surveys that the HEASARC faces
is to ensure that a user can access a sample of all objects of a particular
class.
Assurance is the ability to guarantee both that an observation is
analyzed (and, if appropriate, published), and that unjustified repeat
observations are not made. Observation time on satellites is very limited
(and expensive). Making the data available after some fixed amount of time
ensures that all interested parties in the field get access to that data.
It also ensures that the data are eventually looked at. The issue here is
that in many cases an observation never may be published because the result
is not sufficiently noteworthy. It is essential to provide a simple overview
of the main results of the observation to aviod unnecessary repeated analysis
of the raw data.
Requirements
The four categories of motivations described above and the issues related
to them place the following requirements on the HEASARC:
- the ability to perform multi-mission analysis
- a hierarchical archive structure
- the ability to perform a "quick-look" assessment of the value of data
- vendor-independent data formats
HEASARC Home |
Observatories |
Archive |
Calibration |
Software |
Tools |
Students/Teachers/Public
Last modified: Monday, 19-Jun-2006 11:24:57 EDT
|
