6. C.) Multivariate time series analysis:
An important group of tools to study multivariate time series, like multisensory data or time
sequences of different kinds of spectra, are decomposition techniques. A linear decomposition
technique, based upon the principal component method, is applied to particle energy spectra,
FFT frequency spectra and to wavelet spectra. The method separates different particle
populations and is used to remove instrumental effects on the observed particle energy
spectrum.
In studies of data in the form of point processes, as particle or photon counts, there is an
important question, whether the observed process may be fully described by a Poisson
distribution, or if it is carrying deterministic information. A method, described in two recent
scientific reports, has been developed, to extract the true temporal variations of the photon flux
from the the photon event history observed by the X-ray satellite ROSAT. Also wavelet technique
has been used to study the photon flux variations.
It has been found that introducing the concepts of the non-linear statistics into the signal
processing of infra-acoustic waves, considerable improvements of the results may be obtained.
At present, the angle-of -arrival software was rewritten in such a way that the use of cross-
correlation function was replaced with the entropy based mutual information function.
Another promising technique is filtering of multivariate time series, for example time sequences
of spectra, in the principal component space. The present technique does not distort periodic
or quasi-periodic phenomena present in the data in the same way as the conventional filtering.
NASA’s Big Data Challenge:
NASA’s big data challenge is not just a terrestrial one and it goes beyond the stereotypical
challenge. Many of their “big data” sets are described by significant metadata, but on a scale that
challenges current and future data management practice. Several missions require to regularly
stream data from spacecraft on Earth and in space, faster than we can store, manage, and interpret
it. NASA has two very different types of spacecraft. A deep space spacecraft that sends back data in
the order of MB/s. and earth orbiters that send back data in GB/s. In NASA’s current missions, data
is transferred with radio frequency, which is relatively slow. In the future, NASA will employ
technology such as optical (laser) communication to increase the download and mean a 1000x
increase in the volume of data. This is much more data NASA can handle today and is paring to
tackle future challenges. Currently NASA is planning missions that will easily stream more then
24TB’s a day. That’s roughly 2.4 times the entire Library of Congress – EVERY DAY. For one mission!