Juwvid performs time-frequency analysis. Written in Julia, it uses a modified version of the Wigner distribution, the pseudo Wigner distribution, and the short-time Fourier transform from MATLAB GPL programs, tftb-0.2. The modification includes the zero-padding FFT, the non-uniform FFT, the adaptive algorithm by Stankovic, Dakovic, Thayaparan 2013, the S-method, the L-Wigner distribution, and the polynomial Wigner-Ville distribution.

Jupiter is a multidimensional astrophysical hydrocode. It is based on a Godunov method, and it is parallelized with MPI. The mesh geometry can either be cartesian, cylindrical or spherical. It allows mesh refinement and includes special features adapted to the description of planets embedded in disks and nearly steady states.

Juliet essentially serves as a wrapper of other tools, including Batman (ascl:1510.002), George (ascl:1511.015), Dynesty (ascl:1809.013) and AstroPy (ascl:1304.002), to analyze and model transits, radial-velocities, or both from multiple instruments at the same time. Using nested sampling algorithms, it performs a thorough sampling of the parameter space and a model comparison via Bayesian evidences. Juliet also fits transiting and non-transiting multi-planetary systems, and Gaussian Processes (GPs) which might share hyperparameters between the photometry and radial-velocities simultaneously (e.g., stellar rotation periods).

JUDE (Jayant's UVIT Data Explorer) converts the Level 1 data (FITS binary table) from the Ultraviolet Imaging Telescope (UVIT) on ASTROSAT into three output files: a photon event list as a function of frame number (FITS binary table); a FITS image file with two extensions; and a PNG file created from the FITS image file with an automated scaling.

JSPAM models galaxy collisions using a restricted n-body approach to speed up computation. Instead of using a softened point-mass potential, the software supports a modified version of the three component potential created by Hernquist (1994, ApJS 86, 389). Although spherically symmetric gravitationally potentials and a Gaussian model for the bulge are used to increase computational efficiency, the potential mimics that of a fully consistent n-body model of a galaxy. Dynamical friction has been implemented in the code to improve the accuracy of close approaches between galaxies. Simulations using this code using thousands of particles over the typical interaction times of a galaxy interaction take a few seconds on modern desktop workstations, making it ideal for rapidly prototyping the dynamics of colliding galaxies. Extensive testing of the code has shown that it produces nearly identical tidal features to those from hierarchical tree codes such as Gadget but using a fraction of the computational resources. This code was used in the Galaxy Zoo: Mergers project and is very well suited for automated fitting of galaxy mergers with automated pattern fitting approaches such as genetic algorithms. Java and Fortran versions of the code are available.

JPLephem loads and uses standard Jet Propulsion Laboratory (JPL) ephemerides for predicting the position and velocity of a planet or other Solar System body. It is one of the foundations of the Skyfield (ascl:1907.024) astronomy library for Python, and can also be used as a standalone package to generate raw vectors.

FITS File interaction written in Visual Studio C# .Net.

JPFITS is not based upon any other implementation and is written from the ground-up, consistent with the FITS standard, designed to interact with FITS files as object-oriented structures.

JPFITS provides functionality to interact with FITS images and binary table extensions, as well as providing common mathematical methods for the manipulation of data, data reductions, profile fitting, photometry, etc.

JPFITS also implements object-oriented classes for Point Source Extraction, World Coordinate Solutions (WCS), WCS automated field solving, FITS Headers and Header Keys, etc.

The automatic world coordinate solver is based on the trigonometric algorithm as described here:

https://iopscience.iop.org/article/10.1088/1538-3873/ab7ee8

All function parameters, methods, properties, etc., are coded with XML descriptions which will function with Visual Studio. Other code editors may or may not read the XML files.

Everything which is reasonable to parallelize in order to benefit from the computation speed increase for multi-threaded systems has been done so. In all such cases function options are given in order to specify the use of parallelism or not. Generally, most image manipulation functions are highly amenable to parallelism. No parallelism is forced, i.e., any code which may execute parallelized is given a user option to do so or not.

JoXSZ jointly fits the thermodynamic profiles of galaxy clusters from both SZ and X-ray data using a Markov chain Monte Carlo fitting algorithm. It is an enhanced version of preprofit (ascl:1910.002), which fits only SZ data. JoXSZ parameterizes the pressure and electron density profile of a galaxy cluster with a given center and derives the temperature profile as the ratio of these quantities through the ideal gas law. The X-ray and SZ-based temperatures can be similar or different, which allows study of the cluster elongation along line of sight, gas clumping, or calibration uncertainties.

JOFILUREN analyzes and de-noises scientific data and is useful for studying and reducing the physical effects of particle noise in particle-mesh computer simulations. It uses wavelets, which can efficiently remove noise from cosmological, galaxy and plasma N-body simulations. Written in Fortran, the code is portable and can be included in grid-based N-body codes. JOFILUREN can also be applied for removing noise from standard data, such as signals and images.

jnkepler models photometric and radial velocity data of multi-planet systems via N-body integration. Built with JAX, it leverages automatic differentiation for efficient computation of model gradients. This enables seamless integration with gradient-based optimizers and Hamiltonian Monte Carlo methods, including the No-U-Turn Sampler (NUTS) in NumPyro (ascl:2505.005). jnkepler is particularly suited for efficiently sampling from multi-planet posteriors involving a larger number of parameters and strong degeneracy.

JKTLD outputs theoretically-calculated limb darkening (LD) strengths for equations (LD laws) which predict the amount of LD as a function of the part of the star being observed. The coefficients of these laws are obtained by bilinear interpolation (in effective temperature and surface gravity) in published tables of coefficients calculated from stellar model atmospheres by several researchers. Many observations of stars require the strength of limb darkening (LD) to be estimated, which can be done using theoretical models of stellar atmospheres; JKTLD can help in these circumstances.

The JKTEBOP code is used to fit a model to the light curves of detached eclipsing binary stars in order to derive the radii of the stars as well as various other quantities. It is very stable and includes extensive Monte Carlo or bootstrapping error analysis algorithms. It is also excellent for transiting extrasolar planetary systems. All input and output is done by text files; JKTEBOP is written in almost-standard FORTRAN 77 using first the g77 compiler and now the ifort compiler.

Jitter predicts radial-velocity (RV) jitter due to stellar oscillations and granulation, in terms of various sets of fundamental stellar properties. The code can also be used to set a prior for the jitter term as a component when modeling the Keplerian orbits of the exoplanets.

JHelioview is open source visualization software for solar physics data. The JHelioviewer client application enables users to browse petabyte-scale image archives; the JHelioviewer server integrates a JPIP server, metadata catalog, and an event server. JHelioview uses the JPEG 2000 image compression standard, which provides efficient access to petabyte-scale image archives; JHelioviewer also allows users to locate and manipulate specific data sets.

JexoSim 2.0 (JWST Exoplanet Observation Simulator) simulates exoplanet transit observations using all four instruments of the James Webb Space Telescope, and is designed for the planning and validation of science cases for JWST. The code generates synthetic spectra that capture the full impact of complex noise sources and systematic trends, allowing for assessment of both accuracy and precision in the final spectrum. JexoSim does not contain all known systematics for the various instruments, but is a good starting point to investigate the effects of systematics, and has the framework to incorporate more systematics in the future.

jetsimpy creates hydrodynamic simulations of relativistic blastwaves with tabulated angular energy and Lorentz factor profiles and efficiently models Gamma-Ray Burst afterglows. It supports tabulated angular energy and tabulated angular Lorentz factor profiles. jetsimpy also supports ISM, wind, and mixed external density profile, including synthetic afterglow light curves, apparent superluminal motion, and sky map and Gaussian equivalent image sizes. Additionally, you can add your own emissivity model by defining a lambda function in a c++ source file, allowing the package to be used for more complicated models such as Synchrotron self-absorption.

JetSeT reproduces radiative and accelerative processes acting in relativistic jets and fits the numerical models to observed data. This C/Python framework re-bins observed data, can define data sets, and binds to astropy tables and quantities. It can use Synchrotron Self-Compton (SSC), external Compton (EC) and EC against the CMB when defining complex numerical radiative scenarios. JetSeT can constrain the model in the pre-fitting stage based on accurate and already published phenomenological trends starting from parameters such as spectral indices, peak fluxes and frequencies, and spectral curvatures. The package fits multiwavelength SEDs using both frequentist approach and Bayesian MCMC sampling, and also provides self-consistent temporal evolution of the plasma under the effect of radiative and accelerative processes for both first order and second order (stochastic acceleration) processes.

JETGET accesses, visualizes, and analyses (magnetized-)fluid dynamics data stored in Hierarchical Data Format (HDF) and ASCII files. Although JETGET has been optimized to handle data output from jet simulations using the Zeus code (ascl:1306.014) from NCSA, it is also capable of analyzing other data output from simulations using other codes. JETGET can select variables from the data files, render both two- and three-dimensional graphics and analyze and plot important physical quantities. Graphics can be saved in encapsulated Postscript, JPEG, VRML, or saved into an MPEG for later visualization and/or presentations. The strength of JETGET in extracting the physics underlying such phenomena is demonstrated as well as its capabilities in visualizing the 3-dimensional features of the simulated magneto-hydrodynamic jets. The JETGET tool is written in Interactive Data Language (IDL) and uses a graphical user interface to manipulate the data. The tool was developed on a LINUX platform and can be run on any platform that supports IDL.

Written in Python, JetCurry models the 3D geometry of jets from 2-D images. JetCurry requires NumPy and SciPy and incorporates emcee (ascl:1303.002) and AstroPy (ascl:1304.002), and optionally uses VPython. From a defined initial part of the jet that serves as a reference point, JetCurry finds the position of highest flux within a bin of data in the image matrix and fits along the x axis for the general location of the bends in the jet. A spline fitting is used to smooth out the resulted jet stream.

JET (JWST Exoplanet Targeting) optimizes lists of exoplanet targets for atmospheric characterization by the James Webb Space Telescope (JWST). The software uses catalogs of planet detections, either simulated, or actual and categorizes targets by radius and equilibrium temperature; it also estimates planet masses and generates model spectra and simulated instrument spectra. JET then performs a statistical analysis to determine if the instrument spectra can confirm an atmospheric detection and finally ranks the targets within each category by observation time required for detection.

JEDI searches for and characterizes coronal dimming in light curves produced from the Solar Dynamics Observatory (SDO) Extreme Ultraviolet (EUV) Variability Experiment (EVE). The suite has a wrapper script that calls other functions, which can also be run independently assuming needed inputs from prior functions are provided. JEDI's functions fit light curves and return the best fit, compute precision for iron light curves, and find the biggest dimming depth and its time in a given light curve. JEDI also includes functions for finding the duration of the dimming, minimum, maximum, and mean slope of dimming of a light curve, and for identifying the biggest peak in two light curves, time shifting them so the peaks are concurrent, scaling them so the peaks are the same magnitude, and then subtracting them, among other useful functions.

Jdaviz provides data viewers and analysis plugins that can be flexibly combined as desired to create interactive applications. It offers Specviz (ascl:1902.011) for visualization and quick-look analysis of 1D astronomical spectra; Mosviz for visualization of astronomical spectra, including 1D and 2D spectra as well as contextual information, and Cubeviz for visualization of spectroscopic data cubes (such as those produced by JWST MIRI). Imviz, which provides visualization and quick-look analysis for 2D astronomical images, is also included. Jdaviz is designed with instrument modes from the James Webb Space Telescope (JWST) in mind, but the tool is flexible enough to read in data from many astronomical telescopes, and the documentation provides a complete table of all supported modes.

JCMTDR reduces continuum on-the-fly mapping data obtained with UKT14 or the heterodyne instruments using the IFD on the James Clerk Maxwell Telescope. This program reduces archive data and heterodyne beam maps and was distributed as part of the Starlink software collection (ascl:1110.012).

COADD was used to reduce photometry and continuum data from the UKT14 instrument on the James Clerk Maxwell Telescope in the 1990s. The software can co-add multiple observations and perform sigma clipping and Kolmogorov-Smirnov statistical analysis. Additional information on the software is available in the JCMT Spring 1993 newsletter (large PDF).

JB2008 (Jacchia-Bowman 2008) is an empirical thermospheric density model developed as an improved revision to the Jacchia-Bowman 2006 model, based on Jacchia’s diffusion equations. Driving solar indices are computed from on-orbit sensor data, which are used for the solar irradiances in the extreme through far ultraviolet, including x-ray and Lyman-α wavelengths. Exospheric temperature equations are developed to represent the thermospheric EUV and FUV heating. Semiannual density equations based on multiple 81-day average solar indices are used to represent the variations in the semiannual density cycle that result from EUV heating, and geomagnetic storm effects are modeled using the Dst index as the driver of global density changes.

jaxspec performs statistical inference on X-ray spectra. It loads an X-ray spectrum (in the OGIP standard), defines a spectral model from the implemented components, and calculates the best parameters using state-of-the-art Bayesian approaches. The code is built on top of JAX (ascl:2111.002) to provide just-in-time compilation and automatic differentiation of the spectral models, enabling the use of sampling algorithms. jaxspec is written in pure Python and is not dependent on HEASoft (ascl:1408.004).

jaxoplanet is a functional-programming-forward implementation of many features from the exoplanet and starry packages built on top of JAX (ascl:2111.002). It includes fast and robust implementations of many exoplanet-specific operations, including solving Kepler’s equation, and computing limb-darkened light curves. jaxoplanet has first-class support for hardware acceleration using GPUs and TPUs, and integrates seamlessly with modeling tools such as NumPyro (ascl:2505.005) and Flax (ascl:2504.026).

JAX brings Autograd and XLA together for high-performance machine learning research. It can automatically differentiate native Python and NumPy functions. The code can differentiate through loops, branches, recursion, and closures, and it can take derivatives of derivatives of derivatives. JAX supports reverse-mode differentiation (a.k.a. backpropagation) via grad as well as forward-mode differentiation, and the two can be composed arbitrarily to any order.

JAVELIN (formerly known as SPEAR) is an approach to reverberation mapping that computes the lags between the AGN continuum and emission line light curves and their statistical confidence limits. It uses a damped random walk model to describe the quasar continuum variability and the ansatz that emission line variability is a scaled, smoothed and displaced version of the continuum. While currently configured only to simultaneously fit light curve means, it includes a general linear parameters formalism to fit more complex trends or calibration offsets. The noise matrix can be modified to allow for correlated errors, and the correlation matrix can be modified to use a different stochastic process. The transfer function model is presently a tophat, but this can be altered by changing the line-continuum covariance matrices. It is also able to cope with some problems in traditional reverberation mapping, such as irregular sampling, correlated errors and seasonal gaps.

The Jeans Anisotropic MGE (JAM) modeling method uses the Multi-Gaussian Expansion parameterization for the galaxy surface brightness. The code allows for orbital anisotropy (three-integrals distribution function) and also provides the full second moment tensor, including proper motions and radial velocities.

JAGS analyzes Bayesian hierarchical models using Markov Chain Monte Carlo (MCMC) simulation not wholly unlike BUGS. JAGS has three aims:

- to have a cross-platform engine for the BUGS language;
- to be extensible, allowing users to write their own functions, distributions and samplers; and
- to be a platform for experimentation with ideas in Bayesian modeling.

J-comb combines high-resolution data with large-scale missing information with low-resolution data containing the short spacing. Based on uvcombine (ascl:2208.014), it takes as input FITS files of low- and high-resolution images, the angular resolution of the input images, and the pixel size of the input images, and outputs a FITS file of the combined image.

J plots classifies and quantifies a pixelated structure, based on its principal moments of inertia, thus enabling automatic detection and objective comparisons of centrally concentrated structures (cores), elongated structures (filaments) and hollow circular structures (bubbles) from the main population of slightly irregular blobs that make up most astronomical images. Examples of how to analyze 2D or 3D datasets, enabling an unbiased analysis and comparison of simulated and observed structures are provided along with the Python code.

The simulation and analysis framework ixpeobssim was specifically developed for the Imaging X-ray Polarimetry Explorer (IXPE). It produces realistic simulated observations, in the form of event lists in FITS format, that also contain a strict superset of the information included in the publicly released IXPE data products. The framework's core simulation capabilities are complemented by post-processing applications that support the spatial, spectral, and temporal models needed for analysis of typical polarized X-ray sources, allowing implementation of complex, polarization-aware analysis pipelines. Where applicable, the data formats are consistent with the common display and analysis tools used by the community, e.g., the binned count spectra can be fed into XSPEC (ascl:9910.005), along with the corresponding response functions, for doing standard spectral analysis. All ixpeobssim simulation and analysis tools are fully configurable via the command line.

iWander assesses the origin of interstellar small bodies such as asteroids and comets. It includes a series of databases and tools that can be used in general for studying the dynamics of an interstellar vagabond object (small−body, interstellar spaceship and even stars).

IUEDR reduces IUE data. It addresses the problem of working from the IUE Guest Observer tape or disk file through to a calibrated spectrum that can be used in scientific analysis and is a complete system for IUE data reduction. IUEDR was distributed as part of the Starlink software collection (ascl:1110.012).

ITERA, the IDL Tool for Emission-line Ratio Analysis, is an IDL widget tool that allows you to plot ratios of any strong atomic and ionized emission lines as determined by standard photoionization and shock models. These "line ratio diagrams" can then be used to determine diagnostics for nebulae excitation mechanisms or nebulae parameters such as density, temperature, metallicity, etc. ITERA can also be used to determine line sensitivities to such parameters, compare observations with the models, or even estimate unobserved line fluxes.

ISW and Weak Lensing Likelihood code is the likelihood code that calculates the likelihood of Integrated Sachs Wolfe and Weak Lensing of Cosmic Microwave Background using the WMAP 3year CMB maps with mass tracers such as 2MASS (2-Micron All Sky Survey), SDSS LRG (Sloan Digital Sky Survey Luminous Red Galaxies), SDSS QSOs (Sloan Digital Sky Survey Quasars) and NVSS (NRAO VLA All Sky Survey) radio sources. The details of the analysis (*thus the likelihood code) can be understood by reading the papers ISW paper and Weak lensing paper. The code does brute force theoretical matter power spectrum and calculations with CAMB (ascl:1102.026). See the paper for an introduction, descriptions, and typical results from some pre-WMAP data. The code is designed to be integrated into CosmoMC.

The ISPy3 suite of Python routines models and analyzes integrated-light spectra of stars and stellar populations. The actual spectral modeling and related tasks such as setting up model atmospheres is done via external codes. Currently, the Kurucz codes (ATLAS/SYNTHE) and MARCS/TurboSpectrum are supported, though implementing other similar codes should be relatively straight forward.

iSpec is an integrated software framework written in Python for the treatment and analysis of stellar spectra and abundances. Spectra treatment functions include cosmic rays removal, continuum normalization, resolution degradation, and telluric lines identification. It can also perform radial velocity determination and correction and resampling. iSpec can also determine atmospheric parameters (i.e effective temperature, surface gravity, metallicity, micro/macroturbulence, rotation) and individual chemical abundances by using either the synthetic spectra fitting technique or equivalent widths method. The synthesis is performed with SPECTRUM (ascl:9910.002).

IsoFATE (Isotopic Fractionation via ATmospheric Escape) models mass fractionation resulting from diffusive separation in escaping planetary atmospheres and numerically computes atmospheric species abundance over time. The model is tuned to sub-Neptune sized planets with rocky cores of Earth-like bulk composition and primordial H/He atmospheres. F, G, K, and M type stellar fluxes are readily implemented. IsoFATE has two versions, the first of which simulates a ternary mixture of H, He, and D (deuterium); the second version is coupled to the magma ocean-atmosphere equilibrium chemistry model Atmodeller.

Isochrones, written in Python, simplifies common tasks often done with stellar model grids, such as simulating synthetic stellar populations, plotting evolution tracks or isochrones, or estimating the physical properties of a star given photometric and/or spectroscopic observations.

ISO transforms MESA history files into a uniform basis for interpolation and then constructs new stellar evolution tracks and isochrones from that basis. It is written in Fortran and requires MESA (ascl:1010.083), primarily for interpolation. Though designed to ingest MESA star history files, tracks from other stellar evolution codes can be incorporated by loading the tracks into the data structures used in the codes.

iSLAT (the interactive Spectral-Line Analysis Tool) provides an interactive interface for the visualization, exploration, and analysis of molecular spectra. Synthetic spectra are made using a simple slab model; the code uses molecular data from HITRAN. iSLAT has been tested on spectra at infrared wavelengths as observed at different resolving powers (R = 700-90,000) with JWST-MIRI, Spitzer-IRS, VLT-CRIRES, and IRTF-ISHELL.

ISIS, the Interactive Spectral Interpretation System, is designed to facilitate the interpretation and analysis of high resolution X-ray spectra. It is being developed as a programmable, interactive tool for studying the physics of X-ray spectrum formation, supporting measurement and identification of spectral features, and interaction with a database of atomic structure parameters and plasma emission models.

ISIS is a complete package to process CCD images using the image Optimal subtraction method (Alard & Lupton 1998, Alard 1999). The ISIS package can find the best kernel solution even in case of kernel variations as a function of position in the image. The relevant computing time is minimal in this case and is only slightly different from finding constant kernel solutions. ISIS includes as well a number of facilities to compute the light curves of variables objects from the subtracted images. The basic routines required to build the reference frame and make the image registration are also provided in the package.

iSEDfit uses Bayesian inference to extract the physical properties of galaxies from their observed broadband photometric spectral energy distribution (SED). In its default mode, the inputs to iSEDfit are the measured photometry (fluxes and corresponding inverse variances) and a measurement of the galaxy redshift. Alternatively, iSEDfit can be used to estimate photometric redshifts from the input photometry alone.

After the priors have been specified, iSEDfit calculates the marginalized posterior probability distributions for the physical parameters of interest, including the stellar mass, star-formation rate, dust content, star formation history, and stellar metallicity. iSEDfit also optionally computes K-corrections and produces multiple "quality assurance" (QA) plots at each stage of the modeling procedure to aid in the interpretation of the prior parameter choices and subsequent fitting results. The software is distributed as part of the impro IDL suite.

Isca provides a framework for the idealized modeling of the global circulation of planetary atmospheres at varying levels of complexity and realism. Though Isca is an outgrowth of models designed for Earth's atmosphere, it may readily be extended into other planetary regimes. Various forcing and radiation options are available. At the simple end of the spectrum a Held-Suarez case is available. An idealized grey radiation scheme, a grey scheme with moisture feedback, a two-band scheme and a multi-band scheme are also available, all with simple moist effects and astronomically-based solar forcing. At the complex end of the spectrum the framework provides a direct connection to comprehensive atmospheric general circulation models.

ISAP, written in IDL, simplifies the process of visualizing, subsetting, shifting, rebinning, masking, combining scans with weighted means or medians, filtering, and smoothing Auto Analysis Results (AARs) from post-pipeline processing of the Infrared Space Observatory's (ISO) Short Wavelength Spectrometer (SWS) and Long Wavelength Spectrometer (LWS) data. It can also be applied to PHOT-S and CAM-CVF data, and data from practically any spectrometer. The result of a typical ISAP session is expected to be a "simple spectrum" (single-valued spectrum which may be resampled to a uniform wavelength separation if desired) that can be further analyzed and measured either with other ISAP functions, native IDL functions, or exported to other analysis package (e.g., IRAF (ascl:9911.002), MIDAS (ascl:1302.017) if desired. ISAP provides many tools for further analysis, line-fitting, and continuum measurements, such as routines for unit conversions, conversions from wavelength space to frequency space, line and continuum fitting, flux measurement, synthetic photometry and models such as a zodiacal light model to predict and subtract the dominant foreground at some wavelengths.

iSAP consists of three programs, written in IDL, which together are useful for spherical data analysis. MR/S (MultiResolution on the Sphere) contains routines for wavelet, ridgelet and curvelet transform on the sphere, and applications such denoising on the sphere using wavelets and/or curvelets, Gaussianity tests and Independent Component Analysis on the Sphere. MR/S has been designed for the PLANCK project, but can be used for many other applications. SparsePol (Polarized Spherical Wavelets and Curvelets) has routines for polarized wavelet, polarized ridgelet and polarized curvelet transform on the sphere, and applications such denoising on the sphere using wavelets and/or curvelets, Gaussianity tests and blind source separation on the Sphere. SparsePol has been designed for the PLANCK project. MS-VSTS (Multi-Scale Variance Stabilizing Transform on the Sphere), designed initially for the FERMI project, is useful for spherical mono-channel and multi-channel data analysis when the data are contaminated by a Poisson noise. It contains routines for wavelet/curvelet denoising, wavelet deconvolution, multichannel wavelet denoising and deconvolution.