Can Origins observe exoplanets?
Yes! Origins will will be able to obtain spectra of both transiting and directly imaged exoplanets. The Mid-Infrared Imager, Spectrometer, and Coronograph (MISC) instrument is being designed, in collaboration with JAXA, to conduct transmission and emission (dayside and phase-resolved) spectroscopy of exoplanets, with a particular focus on Earth-sized exoplanets transiting in the habitable zones of M-dwarf stars. By leveraging mass, radius, and density measurements of this population of planets, Origins can pre-select those that are definitively rocky to search for and detect biosignatures, including ozone (O3) and/or nitrous oxide (N2O) with methane (CH4). Due to its low estimated noise floor, Origins observations will also be sufficiently sensitive to measure phase-resolved thermal emission of rocky planets, which will help distinguish between planets with thin or substantial atmospheres. These thermal measurements (with both longitude and altitude) will enable direct determination of habitability.
Origins will also image and characterize the atmospheres of true exoplanet analogs of Jupiter and Saturn, critical for understanding the origin and evolution of exoplanetary systems like our own. Origins will also be capable of imaging young gas giants and ice giants, including those that are temperate (~300 K). For more information about the exoplanet science and technology development enabled by Origins, please see our Exoplanet Flyer.
Given the Herschel discoveries, and the upcoming launch of JWST, are there significant advances to be made with a future IR telescope in the next decade?
Yes! Origins is an exceptionally capable observatory that is significantly more sensitive than Herschel, and covers a much broader infrared wavelength range than JWST. In particular, because Origins is both larger and cooler than Herschel, and it employs much more advanced detector technologies, we expect the spectrometers on OST to be nearly ~1000x more sensitive than those that operated on Herschel, reaching line flux limits of ~3x10-21 W m-2 (5 sigma, 1 hr) at 100 microns.
Similarly, Origins will be >10x more sensitive than JWST beyond 20 microns, where the JWST telescope emission limits the sensitivity. JWST coverage ends at 28 microns, while Origins extends to nearly 600 microns, so Origins can detect the extremely important rest-frame far-infrared cooling lines and dust emission from star forming regions and galaxies in the local Universe, as well as the redshifted rest-frame near and mid-infrared emission from galaxies over a significant fraction of cosmic time.
These huge gains in sensitivity and wavelength coverage over both Herschel and JWST will translate into advances in a wide range of fields, from the study of exoplanet atmospheres, to planet forming disks, to star forming regions in nearby galaxies, the history of heavy-element nucleosythesis, and the growth of galaxies and black holes since Cosmic Dawn.
Can Origins science be done with ALMA?
Because it reaches wavelengths that are much shorter than those of ALMA, OST has access to a large suite of diagnostic features of the atomic and molecular ISM and the dust, that cannot be studied with ALMA over a wide range of Cosmic time. For example, the mid-infrared features (PAH, H2, [NeV], [NeII], [NeIII] and silicate features) are never accessible to ALMA, while the bright far-infrared [OI], [OIII] lines can only be seen in galaxies with z > 3-5. There is some wavelength overlap in the far-IR (above 300 microns), but here, the difference is that OST is being designed to cover large areas of the sky, very efficiently, enabling searches for rare objects at low and high redshift. ALMA is designed to study known objects in great detail, and has very limited ability to map large areas of the sky to find interesting and rare sources. The combination of OST and ALMA will be extremely powerful.
How will the Origins mirror be cooled? What materials will be used?
On Origins, we are using both passive radiation and cryocoolers to achieve a mirror temperature of about 4 K. A multilayer thermal shield is positioned between the telescope and the Sun/Earth/Moon. The layers are reflective in the direction of the Sun, but effectively black in the opposite direction, allowing radiative cooling to deep space. Mechanical cryocoolers provide multi-stage intermediate cooling for the structure and wires spanning the 300 K to 4 K temperatures of the spacecraft to telescope/instruments. Notionally these cooling intercepts will be at about 70 K, 20 K, and 4 K. An innermost shield temperature of about 4-5 K is currently being considered.
The mirror material has not yet been chosen, but leading candidates are aluminum alloy and silicon carbide. An athermal design, using the same material for the backplane mirror support, is also being considered. The goal is to be able to manufacture and test the segments as cheaply as possible, achieving an optical performance that meets the science requirements.
Why make Origins so sensitive when it will be confusion limited?
The first OST design concept should be able to resolve nearly all the Extragalactic Background Light (EBL) in the continuum shortward of 100 microns, and about 50% shortward of 300 microns. However, OST will utilize sensitive wideband spectrometers to map the Universe in three dimensions. The suite of bright mid and far-infrared emission lines and dust features accessible to OST will provide an unambiguous template for source redshift identification, enabling the identification of discrete sources at a much higher spatial density than the traditional confusion limit. A highly sensitive OST will greatly facilitate this mapping of sources in redshift space, enabling us to “beat” the confusion limit, and understand the physical properties of the objects contributing to the EBL.
What kind of orbit will Origins have?
Origins will be deployed to a halo orbit around the Sun-Earth Lagrange 2 (L2) libration point, much like the orbit of NASA’s James Webb Space Telescope, and that being considered for the Wide-Field Infrared Survey Telescope (WFIRST). This destination offers several advantages over other alternatives considered. It is about 1.5 million km away from Earth. At that distance, the environment is thermally benign, and maintaining communication for commanding and data downlink is straightforward. The halo orbit avoids Earth and Moon shadows, so sunlight is always available to provide power, and only a modest amount of propellant is needed to maintain the orbit.
What launch vehicle will Origins use?
Origins, with a 5.9 meter diameter primary mirror, is compatible with NASA’s Space Launch System “Block 1B” when it is equipped with an 8.4-meter diameter fairing. Any launch vehicle that provides comparable payload volume and mass lift capability would suffice.
How will the needed technologies be raised to a sufficiently high Technology Readiness Level (TRL)?
The goal for any of the large astrophysics missions under study is for all key enabling technologies to reach TRL 5 by ~2024. Detector readiness is by far the greatest technology challenge for Origins, as the observatory requires both larger array format and greater per-pixel sensitivity than have yet flown in the far-IR (defined here as 30 microns to ~500 microns). Fortunately, progress in far-IR detectors and readouts has been rapid in the last decade - both the per-pixel sensitivity, and the technology for the large arrays have been demonstrated in laboratory and ground-based astronomy applications. At least four new far-IR detector development proposals were recently selected in the SAT and Astrophysics Research and Analysis (APRA) competitions. These new research programs, combined with other technology studies at JPL and GSFC, will lead to advances in transition edge sensor (TES) bolometers, kinetic inductance detectors (KIDs), and quantum capacitance detectors (QCDs), as well as their readout electronics, which should demonstrate TRL 5. Subsequently, a sustained program will be required to mature one or two of these technologies further for flight on Origins. Finally, the Origins study team is baselining the doped-silicon impurity band detectors (BIBs) used on Spitzer and JWST MIRI for the mid-IR (5-30 micron) instrumentation. An important study question is to assess the stability needed for the Origins exoplanet spectroscopy measurements, and whether the BIB arrays can meet these requirements. The STDT submitted technology gaps (based on the Origins science cases) were submitted to NASA APD, and are now incorporated into the portfolio of technology needs to facilitate maturation.
If SPICA is selected by ESA, will there still be sufficient science that can be achieved with Origins?
SPICA is a mission concept proposed for the latest ESA M5 opportunity. While the science that SPICA could address is similar to what we have outlined for Origins, it is difficult to predict whether or not SPICA will be selected for further study, or placed on track for a launch in the late 2020’s. In it’s current design, SPICA employs a 2.5m, actively cooled telescope and covers a wavelength range of 30-300 microns. OST will be at least 10x more sensitive than SPICA, cover a broader wavelength range, and be significantly faster for blind, wide area spectroscopic surveys. While SPICA would begin to answer some of the key questions that are only addressable with a sensitive, far-infrared space telescope, Origins will be a vastly more capable observatory.