Space Infrared Telescope For Cosmology And Astrophysics Research Articles

Cooling performance of Joule Thomson coolers with straight heat exchangers for space science missions

Space-qualified Joule Thomson coolers with significant cooling power below 5K enable a variety of missions, which include large infrared space telescopes, superconducting detectors for astrophysics, and quantum applications. In JAXA, a 4K-class Joule–Thomson cryocooler (4K-JT) and a 1K-class Joule–Thomson cryocooler (1K-JT) have been developed with the required cooling power of 40mW at 4.5K and 10mW at 1.7K respectively, for upcoming next-generation space missions. This paper reports the results of cooling performance tests of these JT coolers with straight heat exchangers. A straight heat exchanger is desirable in several space science missions, including the Space Infrared Telescope for Cosmology and Astrophysics (SPICA), while the coiled type of heat exchanger was used in past missions. The effectiveness of the heat exchanger is strongly affected by its shape and length, and the effectiveness significantly influences the cooling power and the cooling efficiency of the Joule–Thomson cooler. This study designed, fabricated and measured several types of heat exchanger test models. The effect of gravity and the thermal environment on cooling performance are also reported.

Simulations of the spectral resolving power of a compact space-borne immersion-echelle spectrometer using mid-infrared wave tracing

We performed wave-optics-based numerical simulations at mid-infrared wavelengths to investigate how the presence or absence of entrance slits and optical aberrations affect the spectral resolving power $R$ of a compact, high-spectral-resolving-power spectrometer containing an immersion-echelle grating. We tested three cases of telescope aberration (aberration-free, astigmatism and spherical aberration), assuming the aberration budget of the Space Infrared Telescope for Cosmology and Astrophysics (SPICA), which has a 20-$\mathrm{\mu m}$-wavelength diffraction limit. In cases with a slit, we found that the value of $R$ at around 10--20 $\mathrm{\mu m}$ is approximately independent of the assumed aberrations, which is significantly different from the prediction of geometrical optics. Our results also indicate that diffraction from the slit improves $R$ by enlarging the effective illuminated area on the grating window and that this improvement decreases at short wavelengths. For the slit-less cases, we found that the impact of aberrations on $R$ can be roughly estimated using the Strehl ratio.

The formation of planetary systems with SPICA

Abstract In this era of spatially resolved observations of planet-forming disks with Atacama Large Millimeter Array (ALMA) and large ground-based telescopes such as the Very Large Telescope (VLT), Keck, and Subaru, we still lack statistically relevant information on the quantity and composition of the material that is building the planets, such as the total disk gas mass, the ice content of dust, and the state of water in planetesimals. SPace Infrared telescope for Cosmology and Astrophysics (SPICA) is an infrared space mission concept developed jointly by Japan Aerospace Exploration Agency (JAXA) and European Space Agency (ESA) to address these questions. The key unique capabilities of SPICA that enable this research are (1) the wide spectral coverage $10{-}220\,\mu\mathrm{m}$ , (2) the high line detection sensitivity of $(1{-}2) \times 10^{-19}\,\mathrm{W\,m}^{-2}$ with $R \sim 2\,000{-}5\,000$ in the far-IR (SAFARI), and $10^{-20}\,\mathrm{W\,m}^{-2}$ with $R \sim 29\,000$ in the mid-IR (SPICA Mid-infrared Instrument (SMI), spectrally resolving line profiles), (3) the high far-IR continuum sensitivity of 0.45 mJy (SAFARI), and (4) the observing efficiency for point source surveys. This paper details how mid- to far-IR infrared spectra will be unique in measuring the gas masses and water/ice content of disks and how these quantities evolve during the planet-forming period. These observations will clarify the crucial transition when disks exhaust their primordial gas and further planet formation requires secondary gas produced from planetesimals. The high spectral resolution mid-IR is also unique for determining the location of the snowline dividing the rocky and icy mass reservoirs within the disk and how the divide evolves during the build-up of planetary systems. Infrared spectroscopy (mid- to far-IR) of key solid-state bands is crucial for assessing whether extensive radial mixing, which is part of our Solar System history, is a general process occurring in most planetary systems and whether extrasolar planetesimals are similar to our Solar System comets/asteroids. We demonstrate that the SPICA mission concept would allow us to achieve the above ambitious science goals through large surveys of several hundred disks within $\sim\!2.5$ months of observing time.

Mid-IR cosmological spectrophotometric surveys from space: Measuring AGN and star formation at the cosmic noon with a SPICA-like mission

AbstractWe use the SPace Infrared telescope for Cosmology and Astrophysics (SPICA) project as a template to demonstrate how deep spectrophotometric surveys covering large cosmological volumes over extended fields (1–$15\, \rm{deg^2}$) with a mid-IR imaging spectrometer (17–$36\, \rm{\rm{\upmu m}}$) in conjunction with deep$70\, \rm{\rm{\upmu m}}$photometry with a far-IR camera, at wavelengths which are not affected by dust extinction can answer the most crucial questions in current galaxy evolution studies. A SPICA-like mission will be able for the first time to provide an unobscured three-dimensional (3D, i.e.x,y, and redshiftz) view of galaxy evolution back to an age of the universe of less than$\sim$2 Gyrs, in the mid-IR rest frame. This survey strategy will produce a full census of the Star Formation Rate (SFR) in the universe, using polycyclic aromatic hydrocarbons (PAH) bands and fine-structure ionic lines, reaching the characteristic knee of the galaxy luminosity function, where the bulk of the population is distributed, at any redshift up to$z \sim 3.5$. Deep follow-up pointed spectroscopic observations with grating spectrometers onboard the satellite, across the full IR spectral range (17–$210\, \rm{\rm{\upmu m}}$), would simultaneously measure Black Hole Accretion Rate (BHAR), from high-ionisation fine-structure lines, and SFR, from PAH and low- to mid-ionisation lines in thousands of galaxies from solar to low metallicities, down to the knee of their luminosity functions. The analysis of the resulting atlas of IR spectra will reveal the physical processes at play in evolving galaxies across cosmic time, especially its heavily dust-embedded phase during theactivity peakat the cosmic noon ($z \sim 1$–3), through IR emission lines and features that are insensitive to the dust obscuration.

The role of SPICA-like missions and the Origins Space Telescope in the quest for heavily obscured AGN and synergies with Athena

Abstract In the black hole (BH)–galaxy co-evolution framework, most of the star formation (SF) and the BH accretion are expected to take place in highly obscured conditions. The large amount of gas and dust absorbs most of the UV-to-soft-X radiation and re-emits it at longer wavelengths, mostly in the IR. Thus, obscured active galactic nuclei (AGN) are very difficult to identify in optical or X-ray bands but shine bright in the IR. Moreover, X-ray background (XRB) synthesis models predict that a large fraction of the yet-unresolved XRB is due to the most obscured (Compton thick, CT: N $_{\text{H}}\ge 10^{24} \,\mathrm{cm}^{-2}$ ) of these AGN. In this work, we investigate the synergies between putative IR missions [using SPace Infrared telescope for Cosmology and Astrophysics (SPICA), proposed for European Space Agency (ESA)/M5 but withdrawn in 2020 October, and Origins Space Telescope, OST, as ‘templates’] and the X-ray mission Athena (Advanced Telescope for High ENergy Astrophysics), which should fly in early 2030s, in detecting and characterising AGN, with a particular focus on the most obscured ones. Using an XRB synthesis model, we estimated the number of AGN and the number of those which will be detected in the X-rays by Athena. For each AGN, we associated an optical-to-Far InfraRed (FIR) spectral energy distribution (SED) from observed AGN with both X-ray data and SED decomposition and used these SEDs to check if the AGN will be detected by SPICA-like or OST at IR wavelengths. We expect that, with the deepest Athena and SPICA-like (or OST) surveys, we will be able to photometrically detect in the IR more than 90% of all the AGN (down to $L_{2-10\text{keV}} \sim 10^{42}\,\mathrm{erg\ s}^{-1}$ and up to $z \sim 10$ ) predicted by XRB synthesis modeling, and we will detect at least half of them in the X-rays. The spectroscopic capabilities of the OST can provide ${\approx}51\,000$ and ${\approx}3\,400$ AGN spectra with $R= 300$ at 25–588 $\unicode[Times]{x03BC}$ m in the wide and deep surveys, respectively, the last one up to $z\approx 4$ . Athena will be extremely powerful in detecting and discerning moderate- and high-luminosity AGN, allowing us to properly select AGN even when the mid-IR torus emission is ‘hidden’ by the host galaxy contribution. We will constrain the intrinsic luminosity and the amount of obscuration for $\sim\!20\%$ of all the AGN (and $\sim\!50\%$ of those with $L_{2-10\text{keV}} > 3.2 \times 10^{43}\,\mathrm{erg\ s}^{-1}$ ) using the X-ray spectra provided by Athena WFI. We find that the most obscured and elusive CT-AGN will be exquisitely sampled by SPICA-like mission or OST and that Athena will allow a fine characterisation of the most luminous ones. This will provide a significant step forward in the process of placing stronger constraints on the yet-unresolved XRB and investigating the BH accretion rate evolution up to very high redshift ( $z \ge 4$ ).

Simulating infrared spectro-photometric surveys with a Spritz

AbstractMid- and far-infrared (IR) photometric and spectroscopic observations are fundamental to a full understanding of the dust-obscured Universe and the evolution of both star formation and black hole accretion in galaxies. In this work, using the specifications of the SPace Infrared telescope for Cosmology and Astrophysics (SPICA) as a baseline, we investigate the capability to study the dust-obscured Universe of mid- and far-IR photometry at 34 and$70\, {\rm{\mu }}\mathrm{m}$and low-resolution spectroscopy at$17{-}36\, {\rm{\mu }}\mathrm{m}$using the state-of-the-art Spectro-Photometric Realisations of Infrared-selected Targets at all-z(Spritz) simulation. This investigation is also compared to the expected performance of the Origins Space Telescope and the Galaxy Evolution Probe. The photometric view of the Universe of a SPICA-like mission could cover not only bright objects (e.g.$L_{IR}>10^{12}\,{\rm L}_{\odot}$) up to${z}=10$, but also normal galaxies ($L_{IR}<10^{11}\,{\rm L}_{\odot}$) up to$\textit{z}\sim4$. At the same time, the spectroscopic observations of such mission could also allow us to estimate the redshifts and study the physical properties for thousands of star-forming galaxies and active galactic nuclei by observing the polycyclic aromatic hydrocarbons and a large set of IR nebular emission lines. In this way, a cold, 2.5-m size space telescope with spectro-photometric capability analogous to SPICA, could provide us with a complete three-dimensional (i.e. images and integrated spectra) view of the dust-obscured Universe and the physics governing galaxy evolution up to$\textit{z}\sim4$.

Constraining the Bulk Composition of Disintegrating Exoplanets Using Combined Transmission Spectra from JWST and SPICA

Abstract Disintegrating planets are ultrashort-period exoplanets that appear to have a comet-like dust tail. They are commonly interpreted as low-mass planets whose solid surface is evaporating, and whose tails are made of recondensing minerals. Transmission spectroscopy of the dust tails could thus allow us to directly probe the elementary compositions of these planets. Previous work already investigated the feasibility of such observations using the James Webb Space Telescope (JWST) mid-infrared instrument. In this study, we explore if one can obtain a strong constrain on the tail composition by adding spectroscopy at longer wavelengths using the Space Infrared Telescope for Cosmology and Astrophysics (SPICA) mid-infrared instrument. We use a simple model for the spatial distribution of the dust tails and produce their synthetic transmission spectra assuming various dust compositions. We find that combined infrared spectra from JWST and SPICA will allow us to diagnose various components of the dust tails. JWST will be able to detect silicate and carbide absorption features with a feature-to-noise ratio of ≳3 in the tail transmission spectrum of a disintegrating planet located within 100 pc from the Earth, with a transit depth deeper than 0.5%. SPICA can distinguish between Fe- and Mg-bearing crystalline silicates for planets at ≲100 pc with a transit depth of ≳2%. Transit searches with current and future space telescopes (e.g., TESS and PLATO) will provide ideal targets for such spectroscopic observations.

Cooling capability of JT coolers during the cool-down phase for space science missions

In space science missions that uses cryogen-free mechanical cooler systems to cool the low temperature telescope and detectors, a cooling time from room temperature to low temperature should be considered in the required mission life time, because of a limited cooling power of mechanical cooler. For instance, in the Space Infrared Telescope for Cosmology and Astrophysics (SPICA), the 4K-class Joule Thomson cooler (4K-JT) and the 1K-class Joule Thomson cooler (1K-JT) are being considered to cool a 2.5 m telescope and provide a 1–4 K environment for scientific instruments. The cooling capability of these JT coolers, below 20 K and even lower than 5 K, is critical for initial cooling. The 4K-JT cooling from precooling to operating temperatures under the heat input was measured and confirmed that the 4K-JT has enough cooling power to cool with these heat load. The 1K-JT cool down measurement with heater was also performed. These results enabled us to estimate the cool down time for the heat capacity provided by the telescope and scientific instruments assumed in SPICA, LiteBIRD and the ESA X-ray mission ATHENA.

Constraining the detectability of water ice in debris disks

Context.Water ice is important for the evolution and preservation of life. Identifying the distribution of water ice in debris disks is therefore of great interest in the field of astrobiology. Furthermore, icy dust grains are expected to play important roles throughout the entire planet formation process. However, currently available observations only allow deriving weak conclusions about the existence of water ice in debris disks.Aims.We investigate whether it is feasible to detect water ice in typical debris disk systems. We take the following ice destruction mechanisms into account: sublimation of ice, dust production through planetesimal collisions, and photosputtering by UV-bright central stars. We consider icy dust mixture particles with various shapes consisting of amorphous ice, crystalline ice, astrosilicate, and vacuum inclusions (i.e., porous ice grains).Methods.We calculated optical properties of inhomogeneous icy dust mixtures using effective medium theories, that is, Maxwell-Garnett rules. Subsequently, we generated synthetic debris disk observables, such as spectral energy distributions and spatially resolved thermal reemission and scattered light intensity and polarization maps with our code DMS.Results.We find that the prominent ~3 and 44μm water ice features can be potentially detected in future observations of debris disks with theJames WebbSpace Telescope (JWST) and the Space Infrared telescope for Cosmology and Astrophysics (SPICA). We show that the sublimation of ice, collisions between planetesimals, and photosputtering caused by UV sources clearly affect the observational appearance of debris disk systems. In addition, highly porous ice (or ice-rich aggregates) tends to produce highly polarized radiation at around 3μm. Finally, the location of the ice survival line is determined by various dust properties such as a fractional ratio of ice versus dust, physical states of ice (amorphous or crystalline), and the porosity of icy grains.

The physics of galaxy evolution with SPICA observations

AbstractThe evolution of galaxies at Cosmic Noon (1 < z < 3) passed through a dust-obscured phase, during which most stars formed and black holes in galactic nuclei started to shine, which cannot be seen in the optical and UV, but it needs rest frame mid-to-far IR spectroscopy to be unveiled. At these frequencies, dust extinction is minimal and a variety of atomic and molecular transitions, tracing most astrophysical domains, occur. The Space Infrared telescope for Cosmology and Astrophysics (SPICA), currently under evaluation for the 5th Medium Size ESA Cosmic Vision Mission, fully redesigned with its 2.5-m mirror cooled down to T < 8K will perform such observations. SPICA will provide for the first time a 3-dimensional spectroscopic view of the hidden side of star formation and black hole accretion in all environments, from voids to cluster cores over 90% of cosmic time. Here we outline what SPICA will do in galaxy evolution studies.

Highly sensitive polarimetric camera (B-BOP) for the SPICA mission.

The Space Infrared telescope for Cosmology and Astrophysics (SPICA) mission has just been selected by the European Space Agency as one of the three candidate missions to be further studied for the medium size mission M5. B-BOP, formerly named POL, is one of the three scientific instruments of SPICA which aims, among other scientific goals, to map the galactic filamentary structures and their associated magnetic fields. With a novel interlaced-shaped design, B-BOP will contain 1344 pixels, operating within a temperature range of 50-100mK, covering a 2.6 arcmin field of view, and delivering imaging polarimetry in three spectral bands: 100μm, 200μm, and 350μm simultaneously. In this paper, we investigate by numerical simulations the mechanical, electromagnetic, and thermoelectric behaviors of B-BOP detectors and predict for the three bands (i)a sufficient mechanical stability, (ii)a good electromagnetic absorption higher than 95%, (iii)a high response value better than 1011 V/W, and (iv)especially a very low noise equivalent power reaching 1 aW/Hz1/2 at 50mK.

THE NEXT-GENERATION INFRARED SPACE MISSION SPICA: PROJECT UPDATES

We present project updates of the next-generation infrared space mission SPICA (Space Infrared Telescope for Cosmology and Astrophysics) as of November 2015. SPICA is optimized for mid- and far-infrared astronomy with unprecedented sensitivity, which will be achieved with a cryogenically cooled (below 8 K), large (2.5 m) telescope. SPICA is expected to address a number of key questions in various fields of astrophysics, ranging from studies of the star-formation history in the universe to the formation and evolution of planetary systems. The international collaboration framework of SPICA has been revisited. SPICA under the new framework passed the Mission Definition Review by JAXA in 2015. A proposal under the new framework to ESA is being prepared. The target launch year in the new framework is 2027/28.

DEVELOPMENT OF NEW STITCHING INTERFEROMETRY FOR THE SPICA TELESCOPE

The telescope to be onboard SPICA (Space Infrared Telescope for Cosmology and Astrophysics) has an aperture diameter of 2.5 m and its imaging performance is to be diffraction-limited at a wavelength of <TEX>$20{\mu}m$</TEX> at the operating temperature of <8 K. Because manufacturing precise autocollimating flat mirrors (ACFs) with sizes comparable to the SPICA telescope is not technically feasible, we plan to use sub-aperture stitching interferometry through ACFs for optical testing of the telescope. We have verified the applicability of the sub-aperture stitching technique to the SPICA telescope by performing stitching experiments in a vacuum at a room temperature, using the 800-mm telescope and a 300-mm ACF. We have also developed a new method to reduce uncertainties possibly caused by cryogenic and gravitational deformations of ACFs.

Qualification campaign of the 50 mK hybrid sorption-ADR cooler for SPICA/SAFARI

SAFARI (SpicA FAR-infrared Instrument) is an infrared instrument planned to be part of the SPICA (SPace Infrared telescope for Cosmology and Astrophysics) Satellite. It will offer high spectral resolution in the 30 - 210 μm frequency range. SAFARI will benefit from the cold telescope of SPICA and to obtain the required detectors sensitivity, a temperature of 50 mK is required. This temperature is reached thanks to the use of a hybrid sorption - ADR (Adiabatic Demagnetization Refrigerator) cooler presented here. This cooler provides respectively 14 μW and 0.4 μW of cooling power at 300 mK and 50 mK. The cooler is planned to advantageously use two thermal interfaces of the instrument at 1.8 and 4.9 K. One of the challenges discussed in this paper is the low power available at each intercept. A dedicated laboratory electronic is being designed based on previous development with a particular focus on the 50 mK readout. Temperature regulation at 50 mK is also discussed. This cooler has been designed following flight constraints and will reach a high TRL, including mechanical and environmental tests at the end of the on-going qualification campaign.

Performance Estimation of the Mid-Infrared Camera and Spectrometer Aboard SPICA

The Space Infrared Telescope for Cosmology and Astrophysics (SPICA) is an astronomical mission optimized for mid- and far-infrared astronomy, envisioned for launch in the 2020s. The Mid-infrared Camera and Spectrometer (MCS) is a model instrument that covers the 5–38[Formula: see text][Formula: see text]m wavelength range and enables imaging and spectroscopic observations via four modules named WFC-S, WFC-L, HRS, and MRS. Both of the wide field camera (WFC) modules have a 5-arcmin square field of view (FOV) but cover different wavelength ranges; WFC for the short wavelength region (WFC-S) covers 5 to 24[Formula: see text][Formula: see text]m, whereas WFC for the long wavelength region (WFC-L) covers 18 to 38[Formula: see text][Formula: see text]m. The High Resolution Spectrometer (HRS) covers the 12–18[Formula: see text][Formula: see text]m range with a resolving power of 22,000–30,000, and the Mid Resolution Spectrometer (MRS) performs integral filed units spectroscopy with a 12[Formula: see text] by 8[Formula: see text] FOV. MRS simultaneously covers the 12–38[Formula: see text][Formula: see text]m range with a moderate resolving power of 720–2000. Here, we report sensitivity estimates from a detailed modeling process involving the instrument itself, the telescope, environmental conditions, and the system error budgets. We show that the WFC-S and HRS modules require an adaptive system to correct for telescope pointing error. In particular, band pass filters (BPFs) longer than 26[Formula: see text][Formula: see text]m should be developed.

Preliminary structural design and key technology demonstration of cryogenic assembly in the next-generation infrared space telescope SPICA

The infrared space telescope SPICA (Space Infrared Telescope for Cosmology and Astrophysics) is a next-generation astronomical project of the Japan Aerospace Exploration Agency, which features a 3 m class and 6 K cryogenically cooled space telescope. This paper outlines the current status for the preliminary structural design of the SPICA payload module. Dedicated studies were conducted for key technologies to enhance the design accuracy of the SPICA cryogenic assembly and mitigate the development risk. One of the results is described for the concept of the on-orbit truss separation mechanisms, which aim to both reduce the heat load from the main truss assembly and isolate the microvibration by changing the natural frequency of the spacecraft.

Thermal Property Measurements of Critical Materials for SPICA Payload Module

The Space Infrared Telescope for Cosmology and Astrophysics (SPICA) is a pre-project of JAXA in collaboration with ESA to be launched around 2025. The 3m-class infrared telescope must be below 6K, based on scientific requirements, and features effective radiant cooling into deep space at L2 point combined with a mechanical cooler system in order to cool scientific instruments as well as the telescope. The thermal design of the SPICA payload module must involve researching and measuring the thermophysical properties of materials in order to achieve a highly reliable cooling chain. Accordingly, all critical materials, particularly FRPs were determined and their thermal properties (thermal conductivity, specific heat, and thermal expansion) measured. Subsequently, the measured values were compared with those in literature and included in a thermal model analysis. This paper introduces details of these thermal properties measurements, comparisons with values in literature, and a thermal model analysis of the SPICA payload module.

Thermal study of payload module for the next-generation infrared space telescope SPICA in risk mitigation phase

SPace Infrared telescope for Cosmology and Astrophysics (SPICA) is a pre-project of JAXA in collaboration with ESA to be launched around 2020. The SPICA is transferred into a halo orbit around the second Lagrangian point (L2) in the Sun–Earth system, which enables us to use effective radiant cooling in combination with mechanical cooling system in order to cool a 3m large IR telescope below 6K. At a present, a conceptional study of SPICA is underway to assess and mitigate mission’s risks; the thermal study for the risk mitigation sets a goal of a 25% margin on cooling power of 4K/1K temperature regions, a 25% margin on the heat load from Focal Plane Instruments (FPIs) at intermediated temperature region, to enhance the reliability of the mechanical cooler system, and to enhance feasibility of ground tests. Thermal property measurements of FRP materials are also important. This paper introduces details of the thermal design study for risk mitigation, including development of the truss separation mechanism, the cryogenic radiator, mechanical cooler system, and thermal property measurements of materials.

Exploring the early dust-obscured phase of galaxy formation with blind mid-/far-infrared spectroscopic surveys

While continuum imaging data at far-infrared to sub-millimeter wavelengths have provided tight constraints on the population properties of dusty star forming galaxies up to high redshifts, future space missions like the Space Infra-Red Telescope for Cosmology and Astrophysics (SPICA) and ground based facilities like the Cerro Chajnantor Atacama Telescope (CCAT) will allow detailed investigations of their physical properties via their mid-/far-infrared line emission. We present updated predictions for the number counts and the redshift distributions of star forming galaxies spectroscopically detectable by these future missions. These predictions exploit a recent upgrade of evolutionary models, that include the effect of strong gravitational lensing, in the light of the most recent Herschel and South Pole Telescope data. Moreover the relations between line and continuum infrared luminosity are re-assessed, considering also differences among source populations, with the support of extensive simulations that take into account dust obscuration. The derived line luminosity functions are found to be highly sensitive to the spread of the line to continuum luminosity ratios. Estimates of the expected numbers of detections per spectral line by SPICA/SAFARI and by CCAT surveys for different integration times per field of view at fixed total observing time are presented. Comparing with the earlier estimates by Spinoglio et al. (2012) we find, in the case of SPICA/SAFARI, differences within a factor of two in most cases, but occasionally much larger. More substantial differences are found for CCAT.

THE POTENTIAL FOR DETECTING GAMMA-RAY BURST AFTERGLOWS FROM POPULATION III STARS WITH THE NEXT GENERATION OF INFRARED TELESCOPES

We investigate the detectability of a proposed population of Gamma-Ray Bursts (GRBs) from the collapse of Population III (Pop III) stars. The James Webb Space Telescope (JWST) and Space Infrared telescope for Cosmology and Astrophysics (SPICA) will be able to observe the late time infrared afterglows. We have developed a new method to calculate their detectability, which takes into account the fundamental initial mass function (IMF) and formation rates of Pop III stars, from which we find the temporal variability of the afterglows and ultimately the length of time JWST and SPICA can detect them. In the range of plausible Pop III GRB parameters, the afterglows are always detectable by these instruments during the isotropic emission, for a minimum of 55 days and a maximum of 3.7 years. The average number of detectable afterglows will be 2.96$\times 10^{-5}$ per SPICA field of view (FOV) and 2.78$\times 10^{-6}$ per JWST FOV. These are lower limits, using a pessimistic estimate of Pop III star formation. An optimal observing strategy with SPICA could identify a candidate orphan afterglow in $\sim 1.3$ years, with a 90 percent probability of confirmation with further detailed observations. A beamed GRB will align with the FOV of the planned GRB detector Energetic X-ray Imaging Survey Telescope once every 9 years. Pop III GRBs will be more easily detected by their isotropic emissions (i.e. orphan afterglows) rather than by their prompt emissions.