Fully illuminated Jupiter disk albedo and limb darkening observed by DSCOVR-EPIC from the Earth–Sun Lagrange-1 orbit

Multispectral images of Jupiter were obtained by the Earth polychromatic imaging camera (EPIC) orbiting at the Earth–Sun Lagrange point 1 (L₁) on 15 March 2016 and again on 5 June 2019 using a 30-cm Cassegrain telescope imaging on a 2,048 × 2,048 pixel detector with a 0.62° field of view. The images of Jupiter were obtained using 10 narrow bandpass filters (in the range of 317.5–779.5 nm) that were radiometrically calibrated and designed to have very little out-of-band transmissions. The EPIC instrument was carefully corrected for geometric stray-light effects, pixel non-uniformity (flat fielding), and etaloning (680–780 nm). The Jupiter images were contained in a small disk of diameter 43 pixels near the center of the detector. The resulting images had a spatial resolution of 4,900 km as well as showed clear evidence of limb darkening, the east-west bands, and the red spot of Jupiter. These results were compared with previous measurements from Jupiter filter images obtained by the Hubble space telescope from a ground-based filter instrument at the Tortugas Mountain Observatory operated by New Mexico State University and the portable filter device PlanetCam at Calar Alto Observatory in Spain. The EPIC estimates of the whole-disk albedo are in good agreement with previous high-spectral-resolution spectrometer results (from the European Southern Observatory in La Silla, Chile) in the visible and near-infrared wavelengths but are lower in five ultraviolet (UV) narrow bandpass filter channels (318–388 nm). A possible reason for this disagreement with the spectrometer-estimated UV albedo could be out-of-band stray light from the spectrometer grating. The EPIC observations from L₁ have better spatial resolution than ground-based filter measurements and are expected to provide improved estimates of Jupiter’s limb darkening. Absorption by methane was considered during the measurements, and the current mixing ratio 2 × 10⁻³ is estimated to be insufficient to explain the decrease in albedo between 764 and 779.5 nm unless the reflecting cloud layer is at a pressure of two atmospheres.

1 Introduction

The Deep Space Climate Observatory (DSCOVR) satellite was launched in 2015 to an orbit about the Earth–Sun Lagrange point 1 (L₁) to produce images and science products of the full sunlit Earth and Moon using the Earth polychromatic imaging camera (EPIC) (Supplementary Figure SA1; Herman et al., 2018; Marshak et al., 2018); the data were obtained in 10 narrowband filter channels (Table 1). The EPIC system is based on a 30-cm Cassegrain telescope having a focal length of 2.855 m and imaging on a 2,048-by-2,048-pixel hafnium-coated silicon-based detector whose sensitivity ranges from 300 nm to 1,000 nm. The optical design is such that the sun-illuminated Earth disk almost fills the 0.62° field of view (FOV) and the detector when closest to Earth at approximately 1.5 million kilometers. EPIC has been carefully calibrated and corrected for pixelwise variations (flat fielding), geometric stray light (Cede et al., 2021), and etaloning in the wavelength range of 680–780 nm. The wavelength-dependent geometric stray-light corrections, especially in the ultraviolet (UV) range, are needed for accurate retrieval of the Earth’s total column ozone amounts (Herman et al., 2018; 2025). Because of the Earth observation requirements, the 10 narrowband filters were custom designed to ensure very low amounts of out-of-band interference.

Table 1

Table 1. Wavelength, Δ = full width at half maximum (FWHM), whole-disk pixel image width (in the N-S orientation), and maximum albedo of Jupiter.

Jupiter’s atmosphere has been extensively studied in the 318–780 nm wavelength range of EPIC using both ground-based telescopes and instruments onboard spacecraft. This spectral region includes key absorption bands for methane and ammonia, which are crucial for probing the vertical structure and composition of the planet’s cloud decks. Observations from JunoCam aboard NASA’s Juno spacecraft, particularly its early data from 2016, have provided high-resolution imaging information across multiple wavelengths in this range (Orton et al., 2017). These data reveal that the visibly dark regions in the atmosphere often correspond to bright areas at 5 μm, indicating deeper cloud penetration and lower particulate opacity. Based on data obtained at the European Southern Observatory in La Silla, Chile, Karkoschka (1994) established a detailed albedo spectrum for Jupiter by highlighting strong methane absorption bands near 620, 727, and 890 nm as well as a steep drop in albedo below 400 nm owing to the UV-absorbing chromophores in the upper atmosphere.

The Planetary Data System (PDS) Atmospheres Node (https://pds-atmospheres.nmsu.edu/Jupiter/jupiter.html) has archived spectral data from the Voyager, Galileo, and Cassini missions as well as ground-based telescopic campaigns. These datasets span the UV to near-infrared (NIR) range and include calibrated reflectance spectra that reveal the absorption features from methane, ammonia, and other trace gases. In particular, the 310–400 nm region shows reduced albedo owing to strong UV absorption by stratospheric hazes, while the 400–700 nm region exhibits higher reflectivity dominated by cloud scattering and Rayleigh effects. The red end of the spectrum (700–780 nm) also shows deeper methane absorption bands that partially contribute to the decline in albedo. Overall, the spectral albedo of Jupiter from 318 to 780 nm reflects a balance between gaseous absorption, cloud scattering, and photochemical haze effects (Karkoschka, 1994; 1998). These observations not only inform models of Jupiter’s atmosphere but also serve as critical references for interpreting its reflected light.

The non-Earth observation potential of EPIC is limited to the Moon, Jupiter, and possibly Saturn since the other planets and stars occupy fewer than a sufficient number of pixels on the detector to provide useful data over their required exposure times. The problem here is the small amount of spacecraft pointing jitter that distributes the light from small objects over more than one pixel during the extended exposure times needed for dim targets; this reduces the signal-to-noise ratio (SNR) and spatial resolution. For Jupiter, we temporarily turned off the star tracker during the measurements and relied on the gyroscopes for their ability to propagate a low-noise attitude solution. The EPIC system is always pointed toward Earth so that Venus and Mercury are never in view. Observations from L₁ have the advantage of very good temperature stability since the sun is always at approximately the same angle behind EPIC; the detector degradation (Cede et al., 2021) is also minimal since it is not frequently exposed to energetic particles like the satellites in the low-Earth orbit.

Periodically, Jupiter comes within the permitted viewing range of EPIC when it is near opposition as seen from the Earth (Table 2). However, the opportunities for Jupiter observations are limited since EPIC is restricted to being located within 4° of the spacecraft–Earth line of sight for data communication reasons. Thus, images of Jupiter were obtained on 15 March 2016 and again on 5 June 2019 in 10 narrow wavelength bands (Table 1 and Supplementary Figure SA2) with Δ = full width at half maximum (FWHM). In a 2-h sequence, Jupiter was observed at the 10 bands in exposure intervals ranging from 1 to 8 s each (Table 3). The spatial resolution of EPIC is approximately 1.5 pixels or 0.00045°, with Jupiter’s disk spanning approximately 0.013°.

Table 2

Table 2. Jupiter observation parameters.

Table 3

Table 3. Calibration coefficients at 5.443 AU (2016) and 5.290 AU (2019).

Because the distance of Jupiter from the L₁ orbit is approximately 643–675 million kilometers, the image of Jupiter only occupies a disk of approximately 43 pixels in diameter (Supplementary Figures SA4, SA5) at the center of the charge-coupled device (CCD). Jupiter’s distances from the sun were D_J = 5.442 AU on 15 March 2016 (magnitude: −2.3; phase angle: 10°) and D_J = 5.289 AU on 5 June 2019 (magnitude: −2.5; phase angle: 10°) when the images were obtained by EPIC. Similar measurements were obtained with the Hubble space telescope (HST) (Chanover et al., 1996) on 21 July 1994 at a distance of 5.2 AU (magnitude: −2.6) from the sun. Some of the Hubble filters had central wavelengths that were moderately close to those used by EPIC [(λ, Δ) = (332.7, 33); (450, 50); (545, 49); (560, 60); (727, 2) nm]. However, the HST filters with wider bandwidths included CH₄ and NH₃ absorption features that were not observable with some of the narrowband EPIC filters. Some of the HST (λ = 727 nm, Δ = 2 nm) and EPIC (λ = 779.5 nm, Δ = 1.8 nm) filters were subject to significant CH₄ absorption (Supplementary Figure SA3). We note that there are small disagreements between different references for the parameters noted in Table 2. Jupiter was much brighter by 45% and 74% in 2016 and 2019 when observed by EPIC than by Hubble in 1994, respectively, because of the orbital distance.

The purpose of this study is to estimate Jupiter’s albedo and limb-darkening profile as functions of wavelength, latitude, and relative longitude from EPIC’s counts-per-second information using the calibration coefficients derived for Earth observations and modified to Jupiter’s distance from the sun (Table 3) on the specified dates. The resulting limb-darkening profile and albedo estimates for the central disk meridian on 5 June 2019 are compared with previous results from the HST and ground-based observations from the New Mexico State University Tortugas Mountain Observatory (NMSU) and PlanetCam at Calar Alto Observatory in Spain (Chanover et al., 1996; Mendikoa et al., 2016; 2017). Only one of the PlanetCam observations is used herein (λ = 551 nm, Δ = 88 nm). The EPIC whole-disk albedo results are also compared with the whole-disk high-spectral-resolution ground-based Jupiter albedo measurements from the European Southern Observatory in La Silla, Chile (Karkoschka, 1994; 1998).

2 Materials and methods

The EPIC calibration coefficients to convert level-1a products, measured in counts per second, to albedo obtained for the Earth observations at 1 AU from the sun (Herman et al., 2018; Marshak et al., 2018) need to be modified to Jupiter, which is located at over 5 AU from the sun (Table 3). We note that the albedo estimates are independent of the apparent astronomical magnitude of Jupiter and depend only on its atmospheric conditions at the time of the measurements.

The EPIC Jupiter datasets were created using software that is partially independent of the EPIC Earth processing science pipeline; these differences are as follows. The Jupiter images were calibrated using the standard EPIC level-1a algorithm, which was stored in level-1a files containing the individual exposures (Table 3) and associated metadata. A level-1b file was then created by moving the Jupiter image to the center of the CCD and summing the 1a images to create a single stacked image for each wavelength. This stacking permits creation of an image with improved SNR for each of the 10 wavelength bands (https://zenodo.org/records/15288683).

The images obtained on 15 March 2016 are inclined South and upward by 20.3° relative to the rows and columns of the CCD detector (Figures 1, 3). The latitude scale can be approximately derived from Jupiter’s diameter of 142,984 km across the equator and 133,874 km along a meridian as well as the number of illuminated pixels; this scale can then be corrected for tilt as cosine (20.3°) = 0.938. The set of images obtained on 5 June 2019 are inclined north and upward and do not require a significant tilt correction (Figures 2, 3). The 10 different wavelength images in counts per second are shown in Supplementary Figure SA2. The conversion from the measured counts-per-second data (Equation 1) to Jupiter’s albedo is obtained by multiplying the Earth calibration coefficient K_λ at 1 AU by D_J², where D_J = 5.442 AU (for 15 March 2016) and 5.290 AU (for 5 June 2019). There were 10 exposures per co-added image in 2019 but this number varied in 2016 (Table 3).

$\text{Albedo}={\mathrm{K}}_{\mathrm{\lambda }}\mathrm{C}/\mathrm{N},(1)$

Figure 1

Figure 1. Ten level-1a Earth polychromatic imaging camera (EPIC) images of Jupiter obtained at 512 nm on 15 March 2016 using the exposure intervals listed in Table 2. The southern hemisphere is at the top of each image.

Figure 2

Figure 2. Ten level-1a EPIC images of Jupiter obtained at 512 nm on 5 June 2019 using the exposure intervals listed in Table 3. Note that the assumed north is near the top of each image from 2019 and near the bottom of each image from 2016, with the red spot located in the southern hemisphere. The images are co-added to maximize the signal-to-noise ratio.

Figure 3

Figure 3. Co-added images from Figures 1, 2 magnified to show the CCD pixels relative to the east–west bands of Jupiter. The average distance of Jupiter from L₁ was 4.436 AU. The orientations of the two images are different since the DSCOVR spacecraft rotates by 360° approximately once every 6 months.

where C is the measured number of co-added counts per second in each CCD pixel; N is the number of co-added images (Table 3); K_λ is the conversion coefficient from counts per second to albedo.

3 Results

Figures 1, 2 show the 10 successive images obtained at 512 nm in 2016 and 2019, respectively. The grayscale values of the images are not calibrated accurately even though the underlying numerical counts per second data are calibrated. The most notable difference between these two sets of images is that Jupiter’s axis of rotation is tilted in the 2016 images because of rotation of the DSCOVR spacecraft (approximately one rotation every 6 months); the 2019 images are accidentally almost aligned north–south with the CCD array. The images occupy a disk of approximately 43 pixels in diameter at the center of the 2,048-by-2,048-pixel CCD array (Table 1 and Supplementary Figures SA4, SA5). The 10 images in each set were co-aligned and added together to increase the SNR by a factor of 3.16 (Figure 3). The effects of limb darkening are easily seen in the images of Jupiter’s atmosphere that is mainly composed of H₂ (89.7%; Gautier et al., 1981) and He (10.36%; Niemann et al., 1998), along with small amounts of CH₄ (0.2%; Niemann et al., 1998) and NH₃ (0.02%; Lindal et al., 1981). More details regarding Jupiter’s atmosphere are available in Taylor et al. (2004). The HST wavelength-filtered images of Jupiter at 395 and 631 nm are available in Simon et al. (2015). Note that the total H + He amount without uncertainty estimates exceeds 100%.

Jupiter’s great red spot shown in Figures 1–3 (and for all 10 wavelengths in Supplementary Figure SA2) is a powerful storm located in the southern hemisphere at approximately 22° south from the equator. This places Jupiter’s north pole geographically north of the great red spot, as shown in Figure 3, with approximately 90° north at the top of the 2019 image. The individual CCD pixels are visible in the images.

4 Discussion

Figure 4 shows the estimated Jupiter albedo (Equation 1) for each of the 10 wavelength bands based on a 100-by-100-pixel subset (see Supplementary Figures SA4, SA5) of the CCD array. The abscissa is directed approximately north–south in Figure 4 and east–west in Figure 5. The maximum albedo is determined from the data shown in Figure 4 and listed in column 4 of Table 1. The effect of the band structure on Jupiter’s albedo is clearly observable from the peaks of the albedo plots. The EPIC albedo data as a function of latitude and longitude can be converted to whole-disk albedo as shown later. The outer envelopes are mostly from the central longitudes of the observed disks. Except for small amounts of noise in the 317.5 and 325 nm channels, the dark-space noise level is negligible beyond Jupiter’s limb.

Figure 4

Figure 4. North–south scans are shown in pixel latitude row numbers, while east–west scans are shown in longitude column numbers for the 10 wavelength bands. The outer envelopes in the images are mostly the central longitudes of the observed disks of Jupiter. There are small amounts of noise in the 317.5 and 325 nm ultraviolet channels that are visible in the tails outside the disks, but such noise is negligible in the longer wavelengths.

Figure 5

Figure 5. Jupiter’s albedo at 512 nm on 5 June 2019 plotted as a function of the CCD columns (longitude). The signal-to-noise ratio is sufficient to detect dark-space noise (approximately 300:1), as shown by the tails outside the Jupiter disk region.

Figure 5 shows the 551-nm channel data transposed to plot the albedo as a function of the CCD columns or Jupiter’s longitude (east–west). Of note is the lack of Jupiter’s band features in the east–west plots in Figures 5, 6. The pixel width of Jupiter’s disk is slightly larger in the equatorial direction (44 pixels) than the north–south direction (42 pixels). The equatorial diameter at 1 bar is estimated to be 142,984 km while the polar diameter is 133,708 km (Ridpath, 2012), suggesting that a single pixel represents 142,984/44 = 3,249.63 km equatorially and 133,708/42 = 3,283.52 km meridionally, with a difference of approximately 1%. The average distance per pixel is thus 3,266.41 km, with a spatial resolution of approximately 1.5 pixels or 4,899 km.

Figure 6

Figure 6. Plot of the 551-nm albedo as a function of the approximate latitude and relative longitude based on a spherical coordinate projection of the (x, y) CCD pixel coordinates onto a sphere (x_s, y_s, z_s). Jupiter’s red spot was near the center of the relative longitude scale in 2019, as shown in Figure 2. The outer envelope is given by the meridional line (left panel) passing through the center of the 2019 image in Figure 2 and the equatorial line (right panel).

Figure 6 shows approximate latitude–longitude scales based on a spherical geometric projection of the x–y CCD plane onto a sphere (Equations 2–6), where Jupiter’s red spot on 5 June 2019 is arbitrarily located at −95° relative longitude near the center of the image, as shown in Figure 3.

The spherical coordinate projection from the flat plane of the CCD image (x, y) onto a sphere (x_s, y_s, z_s) of radius R is accomplished using Equations 2–4:

${\mathrm{x}}_{\mathrm{s}}=2\text{Rx}/\left({\mathrm{R}}^2+{\mathrm{x}}^2+{\mathrm{y}}^2\right);(2)$

${\mathrm{y}}_{\mathrm{s}}=2\text{Ry}/\left({\mathrm{R}}^2+{\mathrm{x}}^2+{\mathrm{y}}^2\right);(3)$

${\mathrm{z}}_{\mathrm{s}}=\mathrm{R}\left({\mathrm{R}}^2-{\mathrm{x}}^2-{\mathrm{y}}^2\right).(4)$

Then, the latitude θ and longitude ϕ are given by Equations 5, 6:

$\mathrm{\theta }=\arcsin \left({\mathrm{z}}_{\mathrm{s}}/\mathrm{R}\right);(5)$

$\mathrm{\varphi }=\arctan \left({\mathrm{y}}_{\mathrm{s}}/{\mathrm{x}}_{\mathrm{s}}\right)\text{\hspace{0.17em}adjusted\hspace{0.17em}for\hspace{0.17em}quadrant}+\text{shift}.(6)$

The central meridian (λ = 551 nm, Δ = 3 nm) albedo from Figure 6 can be compared to a similar plot obtained from the HST data on 21 July 1994 (Chanover et al., 1996) at λ = 545 nm (Δ = 48 nm). The equatorial value of the EPIC albedo is 33% higher than that obtained with the HST data. Integrating the corresponding albedo curves shows that the EPIC albedo was 66% higher than that of Hubble. Further comparisons are shown with the ground-based measurements obtained from the Tortugas Mountain Observatory at λ = 560 nm (Δ = 60 nm) on 20 July 1994 (Chanover et al., 1996) as well as the average of four λ = 551 nm (Δ = 88 nm) images acquired with the PlanetCam2 configuration of the 2.2-m telescope at Calar Alto Observatory from 2012 to 2016 (Mendikoa et al., 2017). An additional latitude correction was given by Chanover et al. (1996) to correct for the ellipsoidal nature of Jupiter (Equation 2 in their work). Comparisons of the EPIC observations with those from the HST, PlanetCam, and NMSU are shown in Figure 7 for two wavelength groups, namely, blue (410–450 nm) and green (551–560 nm), along Jupiter’s central meridian as observed on the specified dates. The small FWHM values of the EPIC filters as compared to the much larger FWHM used by the HST and ground-based telescopes can interfere with the estimated albedo comparisons. The limb-darkening slopes seen by EPIC are steeper than those seen by the HST and ground-based measurements from PlanetCam and NMSU.

Figure 7

Figure 7. (a) EPIC central meridian (λ = 551 nm, Δ = 3 nm) albedo on 5 June 2019 as compared to those from the Hubble space telescope (HST; λ = 545 nm, Δ = 49 nm) on 21 July 1994 (Chanover et al., 1996), Tortugas Mountain Observatory (NMSU; λ = 560 nm, Δ = 60 nm) on 20 July 1994 (Chanover et al., 1996), and average of four measurements from PlanetCam (λ = 551 nm, Δ = 88 nm) over 2012–2016 (Mendikoa et al., 2017). (b) Data are similar to those of (a) but shown for the blue wavelength channels for HST (λ = 410 nm, Δ = 14.7 nm) (Chanover et al., 1996) and NMSU (λ = 450 nm, Δ = 100 nm) (Mendikoa et al., 2017).

The measurements acquired by HST at 545 ± 45 nm appear to be low outliers compared to those from EPIC, PlanetCam, and NMSU. Exact comparisons between PlanetCam at 551 ± 88 nm and NMSU at 560 ± 60 nm are not possible because of differences in the filter widths and central wavelengths compared to the well-calibrated EPIC instrument at 551 ± 3 nm. The 551-nm PlanetCam image of Jupiter has a lower spatial resolution than that of EPIC (see the upper left part of Figure 16 in Mendikoa et al., 2016), which results in a more diffuse (broader) sensing of the limb darkening. Judging by the central meridian reflectivity curves, the data from Tortugas Mountain (Figure 1 of Chanover et al., 1996) have a lower spatial resolution than that from EPIC (Figure 7). The EPIC system is corrected for geometric stray light (Cede et al., 2021), which enables accurate estimation of Jupiter’s limb within its spatial resolution (1.5/43 pixels = 3.5% of Jupiter’s disk).

The wavelength dependence of the albedo for the central meridian is shown in Figure 8a as a function of the latitude; the maximum albedo occurs at 680 nm at the equator. The EPIC wavelengths longer than 688.75 nm are affected by methane absorption (Karkoschka, 1998; see also Supplementary Figure SA3). The apparent asymmetry (Figure 8b) between the southern and northern hemispheres is evident in the images shown in Figures 5, 6 and Supplementary Figure SA2 and is an atmospheric property.

Figure 8

Figure 8. (a) Wavelength dependence of Jupiter’s albedo as a function of latitude for the central meridian as seen by EPIC at a longitude of approximately −100°W (Figure 6). (b) Vertical slices through (a) at the specified latitudes smoothed with a spline function.

Karkoschka (1998) estimated the whole-disk albedo of Jupiter, which can be compared with that derived from EPIC (Figure 9). These data are in good agreement in the visible and NIR regions but not in the UV range, where the EPIC estimate of the narrowband whole-disk albedo is smaller. The EPIC data agreement with that of Karkoschka (1998) in the visible wavelength range is comparable to that reported for PlanetCam (Figure 12 in Mendikoa et al., 2017). The apparent spatial resolution of EPIC appears to be better than that of the telescope-spectrometer instrument at the European Southern Observatory in La Silla, Chile (Figure 6 in Karkoschka, 1998).

Figure 9

Figure 9. Comparisons between the whole-disk Jupiter albedo estimates obtained for 1993 and 1995 reported by Karkoschka (1994), Karkoschka (1998) and the EPIC-based whole-disk albedo (small stars).

A possible reason for the UV spectrometer results of Karkoschka (1994), Karkoschka (1998) being larger than the measurements of the EPIC filters is scattering of stray light from the visible wavelength channels into the UV range. This is a common problem with spectrometer measurements, especially given the large dynamic range between the sun’s visible wavelengths and the UV regime (Tzortziou et al., 2012). This form of out-of-band stray light is minimized in the custom-designed EPIC filters (Herman et al., 2018).

The measurements from the European Southern Observatory in La Silla (Chile) and EPIC (Figure 9) suggest that there is either absorption by the atmosphere of Jupiter (composed of 89.7% H₂ and 10% He by volume along with trace amounts of compounds like methane, ammonia, and water) or a decrease in cloud reflectivity between 764 and 779.5 nm. Methane is known to absorb light in this wavelength range but is estimated to cause a decrease of less than 11% (see Supplementary Equations SA1, SA2), which is too small to explain the observed decrease between 764 and 779.5 nm.

5 Summary

The EPIC images of Jupiter in each of 10 wavelength bands obtained on 5 June 2019 were used to estimate Jupiter’s limb darkening and whole-disk albedo at a spatial resolution of 1.5 pixels out of the 43-pixel-span of the disk, with an effective spatial resolution of approximately 4,900 km. This resolution is sufficient to observe Jupiter’s red spot that extends across 16,350 km (Figure 2). Furthermore, the images show visible darker and brighter east–west bands circling Jupiter in the northern and southern midlatitudes. These bands clearly feature in Jupiter’s estimated albedo as a function of the latitude and longitude. There is a notable asymmetry between the hemispheres, with the southern hemisphere being brighter.

EPIC’s radiometric calibrations are based on frequent Earth observations over its current 10-year operating life compared to the well-calibrated low-Earth orbiting satellites, including repeated corrections for flat fielding and geometric stray light. In addition, the flat-field corrections have been performed based on both laboratory measurements and frequent lunar observations. The resulting Earth-atmosphere-derived calibration coefficient K_λ that converts the measured counts-per-second information to albedo was used to correct for Jupiter’s distance from the sun (Table 3). The fact that the Jupiter images occupy only a small central portion of 43 pixels of the 2,048 pixels of the optical FOV indicates that the optical aberrations are minimal.

Comparisons of the EPIC-derived albedo with published albedo from the HST (Chanover et al., 1996) show significant disagreement at green wavelengths (545 nm vs. 551 nm) but agree more closely at blue wavelengths (410 nm vs. 443 nm) (Mendikoa et al., 2017). EPIC also shows greater agreement with the results from PlanetCam and the filter instrument at Tortugas Mountain (NMSU).

EPIC estimates of the Jupiter’s whole-disk albedos were compared with high-spectral-resolution data reported by Karkoschka (1994), Karkoschka (1998), which show good agreement in the visible and NIR wavelengths but lower values in the EPIC UV channels (318–388 nm). A possible reason for the higher spectrometer-estimated UV albedo compared to the EPIC filters is out-of-band stray light. The combination of better spatial resolution than ground-based telescopes, EPIC corrections for spatial stray light, and lack of spectral out-of-band stray light suggest that EPIC’s estimates of narrowband limb darkening as a function of wavelength are accurate to within its spatial resolution. Both Karkoschka (1994), Karkoschka (1998) and EPIC observations show a decrease in albedo between 764 and 779.5 nm that is consistent with methane absorption under the condition that the reflective cloud deck is at a pressure of 2 atm.

Data availability statement

The datasets presented in this study can be found in online repositories. The names of the repository/repositories and accession number(s) can be found at: https://web.archive.org/web/20070607233022/http:/astro.nmsu.edu/∼nchanove/jupcal/jupitercal.html; https://doi.org/10.5281/zenodo.16754674.

Author contributions

JH: Formal analysis, Writing – review and editing, Investigation, Writing – original draft. KB: Data curation, Writing – review and editing, Investigation.

Funding

The author(s) declared that financial support was received for this work and/or its publication. This work was supported by the DSCOVR-EPIC project at the NASA Goddard Space Flight Center.

Conflict of interest

The author(s) declared that this work was conducted in the absence of any commercial or financial relationships that could be construed as a potential conflict of interest.

Generative AI statement

The author(s) declared that generative AI was not used in the creation of this manuscript.

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Supplementary material

The Supplementary Material for this article can be found online at: https://www.frontiersin.org/articles/10.3389/frsen.2025.1685883/full#supplementary-material

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