Edustar Software Catalogue

[Shane Rouse]

The methods here are not specific to the Gaia mission, but the parameters of the functions and their units are specified in a form that is convenient for use with Gaia data, in particular the gaia_source catalogue available from and copies or mirrors.

Functions are provided for converting the astrometric parameters contained in the Gaia catalogue to ICRS Cartesian position (XYZ) and velocity (UVW) vectors. Functions are also provided to convert these vectors between ICRS and Galactic or Ecliptic coordinates. The calculations are fairly straightforward, and follow the equations laid out in section 1.5.6 of The Hipparcos and Tycho Catalogues, ESA SP-1200 (1997) and also section 3.1.7 of the Gaia DR2 documentation (2018).

These functions will often be combined; for instance to calculate the position and velocity in galactic coordinates from Gaia catalogue values, the following expressions may be useful: xyz_gal = icrsToGal(astromXYZ(ra,dec,parallax)) uvw_gal = icrsToGal(astromUVW(array(ra,dec,parallax,pmra,pmdec,radial_velocity))) though note that these particular examples simply invert parallax to provide distance estimates, which is not generally valid. Note also that these functions do not attempt to correct for solar motion. Such adjustments should be carried out by hand on the results of these functions if they are required.

Functions for calculating errors on the Cartesian components based on the error and correlation quantities from the Gaia catalogue are not currently provided. They would require fairly complicated invocations. If there is demand they may be implemented in the future.

The functions provided here correspond to calculations from Astraatmadja & Bailer-Jones, "Estimating Distances from Parallaxes. III. Distances of Two Million Stars in the Gaia DR1 Catalogue", ApJ 833, a119 (2016) 2016ApJ...833..119A based on the Exponentially Decreasing Space Density prior defined therein. This implementation was written with reference to the Java implementation by Enrique Utrilla (DPAC).

These functions are parameterised by a length scale L that defines the exponential decay (the mode of the prior PDF is at r=2L). Some value for this length scale, specified in parsec, must be supplied to the functions as the lpc parameter.

Note that the values provided by these functions do not match those from the paper Bailer-Jones et al. "Estimating Distances from Parallaxes IV: Distances to 1.33 Billion stars in Gaia Data Release 2", accepted for AJ (2018) arXiv:1804.10121. The calculations of that paper differ from the ones presented here in several ways: it uses a galactic model for the direction-dependent length scale not currently available here, it pre-applies a parallax correction of -0.029mas, and it uses different uncertainty measures and in some cases (bimodal PDF) a different best distance estimator.

The Gaia source catalogue provides, for at least some sources, the six-parameter astrometric solution (Right Ascension, Declination, Parallax, Proper motion in RA and Dec, and Radial Velocity), along with errors on these values and correlations between these errors. While a crude estimate of the position at an earlier or later epoch than that of the measurement can be made by multiplying the proper motion components by epoch difference and adding to the measured position, a more careful treatment is required for accurate propagation between epochs of the astrometric parameters, and if required their errors and correlations. The expressions for this are set out in section 1.5.5 (Volume 1) of The Hipparcos and Tycho Catalogues, ESA SP-1200 (1997) (but see below), and the code is based on an implementation by Alexey Butkevich and Daniel Michalik (DPAC). A correction is applied to the SP-1200 treatment of radial velocity uncertainty following Michalik et al. 2014 2014A&A...571A..85M because of their better handling of small radial velocities or parallaxes.

This convenience function just invokes the 7-argument astromUVW function using the inverted parallax for the radial distance, and without invoking the Doppler correction. It is exactly equivalent to: astromUVW(a[0], a[1], a[3], a[4], a[5], 1000./a[2], false) Note this naive inversion of parallax to estimate distance is not in general reliable for parallaxes with non-negligable errors.

The radial distance must be supplied using the r_parsec parameter. A naive estimate from quantities in the Gaia source catalogue may be made with the expression 1000./parallax, though note that this simple inversion of parallax is not in general reliable for parallaxes with non-negligable errors.

The calculations are fairly straightforward, following Eq. 1.5.74 from the Hipparcos catalogue. A (usually small) Doppler factor accounting for light-time effects can also optionally be applied. The effect of this is to multiply the returned vector by a factor of 1/(1-radial_velocity/c), as discussed in Eq. 1.2.21 of the Hipparcos catalogue.

This is clearly an unwieldy function to invoke, but if you are using it with the gaia_source catalogue itself, or other similar catalogues with the same column names and units, you can invoke it by just copying and pasting the example shown in this documentation.

This transformation is only applicable for radial velocities determined independently of the astrometry, such as those obtained with a spectrometer. It is not applicable for the back-transformation of data already propagated to another epoch.

The Easy Spelling Aid and Easy Dyslexia Aid app is ideal in group activities when students are learning new words and the iPad is shared amongst the group. Each student has a turn sounding a new word and sharing the spelling results and pronunciation of that word with the group. Each word is then written down 3 times and repeated by all the students before passing it onto the next student to continue with a new word. Depending on the amount of students in the group (5 or 10), this activity greats a team dynamic, encouraging students to work and feel confident in themselves and as a team.

Easy Spelling Aid boasts a number of benefits for older students and adults. Our app supports multiple languages, rendering it the perfect companion for second language students of all ages and their teachers.

A copy/define/share function for spelling results. Copy and paste you spoken word or phrase directly into another application. Alternatively share will open the activity popup displaying the available apps for immediate pasting. The define function prompts the device dictionary to open, displaying a definition of the highlighted word.

Easy Spelling Aid includes a revolutionary Translator supporting multiple languages and Reverse Translation option. The Reverse Translation option is very handy and quick when communicating in another language. Simply select the Reverse Translation button to reverse the selected languages.

Easy Spelling Aid includes a History Log that automatically saves spelling results, including translations. With the addition of the Easy Spelling Aid Translator and History Log, Easy Spelling Aid is now the perfect learning and travel companion for students of all ages, from 5 to 55 and beyond!

We are proud partners with the Educational App Store and Samsung UK; working with them to create an improved learning experience for school pupils. Samsung are at the forefront of tablet technology in the classroom and supporting teachers in creating interactive environments which are conducive to personalised learning. They visit thousands of schools in the UK and work with them to incorporate tablets, interactive whiteboards and more. Through our partnership, the Educational App Store and Samsung UK visit many schools to recommend them the highest quality, curriculum-aligned apps held within the Curriculum Gateway. Easy Spelling Aid has made it into the Curriculum Gateway and a teacher applan has been created, which is a plan for teachers and schools who download the app to have an idea of how it can be used. #ukedchat

The Easy Spelling Aid app empowers pupils to independently spell word and phrases. Easy Spelling Aid is actually much more than a spelling and reading helper, it is a very special go-to literacy and learning tool that defeats dyslexia and dysgraphia through the use of coloured overlays and special fonts. Also, beyond giving pupils instant help to spelling problematic words, it is a friend to children at the primary level from all backgrounds because it boasts superior and accurate fine-tuned speech recognition in multiple languages.

Through this educationally compelling app, young pupils everywhere are starting to enjoy the benefits of self-directed learning by not having to wait for help from teachers or parents, which is a big plus. Easy Spelling Aid has the potential to be a powerful learning and teaching tool in the classroom.

Easy Spelling Aid has been added to the reviewed apps on the Early Childhood and School Education Group DET, iPads for learning website: iPads for Education and the eduSTAR catalogue, for Victorian schools.

Our entry in the NSIP Interoperability Challenge was successful. The NSIP Interoperability Challenge at EduTECH is an opportunity to showcase the best and most exciting developments in education technology. We demonstrated the Easy Spelling Aid app to the CIOs of every state, territory and sector and received a great response and high level of interest. Thank for selecting or entry.

c80f0f1006