Abstract
The NASA Double Asteroid Redirection Test spacecraft successfully impacted the Didymos–Dimorphos binary asteroid system on 2022 September 26 UTC. We provide an update to its preimpact mutual ...orbit and estimate the postimpact physical and orbital parameters, derived using ground-based photometric observations taken from 2022 July to 2023 February. We found that the total change of the orbital period was −33.240 ± 0.072 minutes (all uncertainties are 3
σ
). We obtained the eccentricity of the postimpact orbit to be 0.028 ± 0.016 and the apsidal precession rate was 7.3 ± 2.0 degrees day
−1
from the impact to 2022 December 2. The data taken later in 2022 December to 2023 February suggest that the eccentricity dropped close to zero or the orbit became chaotic approximately 70 days after the impact. Most of the period change took place immediately after the impact, but in the few weeks following the impact it was followed by an additional change of
−
27
−
58
+
19
s or −19 ± 18 s (the two values depend on the approach we used to describe the evolution of the orbital period after the impact—an exponentially decreasing angular acceleration or the assumption of a constant orbital period, which changed abruptly some time after the impact, respectively). We estimate the preimpact Dimorphos–Didymos size ratio was 0.223 ± 0.012 and the postimpact is 0.202 ± 0.018, which indicate a marginally significant reduction of Dimorphos’ volume by (9 ± 9)% as the result of the impact.
Abstract The Double Asteroid Redirection Test (DART) mission impacted Dimorphos, the satellite of binary near-Earth asteroid (65803) Didymos, on 2022 September 26 UTC. We estimate the changes in the ...orbital and physical properties of the system due to the impact using ground-based photometric and radar observations, as well as DART camera observations. Under the assumption that Didymos is an oblate spheroid, we estimate that its equatorial and polar radii are 394 ± 11 m and 290 ± 16 m, respectively. We estimate that the DART impact instantaneously changed the along-track velocity of Dimorphos by −2.63 ± 0.06 mm s −1 . Initially, after the impact, Dimorphos’s orbital period had changed by −32.7 minutes ± 16 s to 11.377 ± 0.004 hr. We find that over the subsequent several weeks the orbital period changed by an additional 34 ± 15 s, eventually stabilizing at 11.3674 ± 0.0004 hr. The total change in the orbital period was −33.25 minutes ±1.5 s. The postimpact orbit exhibits an apsidal precession rate of 6.7 ± 0.°2 day −1 . Under our model, this rate is driven by the oblateness parameter of Didymos, J 2 , as well as the spherical harmonics coefficients, C 20 and C 22 , of Dimorphos’s gravity. Under the assumption that Dimorphos is a triaxial ellipsoid with a uniform density, its C 20 and C 22 estimates imply axial ratios, a / b and a / c , of about 1.3 and 1.6, respectively. Preimpact images from DART indicate Dimorphos’s shape was close to that of an oblate spheroid, and thus our results indicate that the DART impact significantly altered the shape of Dimorphos.
Abstract On 2022 September 26 (UTC), NASA's Double Asteroid Redirection Test (DART) mission achieved a successful impact on Dimorphos, the secondary component of the near-Earth binary asteroid system ...(65803) Didymos. Subsequent ground-based observations suggest a significant reshaping of Dimorphos, with its equatorial axis ratio changing from 1.06 to ∼1.3. Here we report the effects of this reshaping event on Dimorphos's orbit and attitude. Given the reported reshaping magnitude, our mutual dynamics simulations show that approximately 125 s of the observed 33 minute orbit period change after the DART impact may have resulted from reshaping. This value, however, is sensitive to the precise values of Dimorphos's post-impact axis ratios and may vary by up to 2 times that amount, reaching approximately 250 s within the current uncertainty range. While the rotational state of the body is stable at the currently estimated axis ratios, even minor changes in these ratios or the introduction of shape asymmetry can render its attitude unstable. The perturbation to Dimorphos’s orbital and rotational state delivered by the impact directly, combined with any reshaping, leads to a strong possibility for a tumbling rotation state. To accurately determine the momentum enhancement factor ( β ) through measurements by the European Space Agency’s Hera spacecraft and to evaluate the effectiveness of the kinetic deflection technique for future planetary defense initiatives, the effects of reshaping should not be overlooked.
The shape and rotation of asteroid 2008 TC3 SCHEIRICH, Peter; ĎURECH, Josef; PRAVEC, Petr ...
Meteoritics & planetary science,
10/2010, Letnik:
45, Številka:
10-11
Journal Article
Recenzirano
Odprti dostop
– On October 6, 2008, a small F‐class asteroid 2008 TC3 was discovered by Catalina Sky Survey telescope, and exploded 20 hr later in the Earth’s atmosphere at 37 km altitude. We analyzed available ...photometric data taken from 6 October 21:10 to 7 October 01:46 UT, and created a numerical model of a shape and rotation state of the asteroid. The asteroid was in excited rotational state. We found two approximately mirror solutions of orientation of its angular momentum vector. Rotational and precession periods are 99.20 and 97.00 s (errors of the rotational period for the two solutions are 0.03 and 0.04 s; of the precession period are 0.05 s for both solutions). The volume of the convex model and the length of the longest axis of the dynamically equivalent, equal volume ellipsoid are and , where pV is surface geometric albedo. Assuming a mean albedo value for F taxonomic class, 0.049 ± 0.010, the volume is (25 ± 10) m3 and the longest axis is (6.7 ± 0.8) m. This volume of the convex model is an upper limit on a real volume of the asteroid, which may be less by up to 20% due to concavities.
– A calibrated lightcurve is presented of the near‐Earth asteroid 2008 TC3, obtained before it impacted Earth on October 7, 2008. The asteroid was observed in unfiltered images from the end of ...astronomical twilight until the object entered Earth’s shadow about 2 h later. The observations covered a wide range of phase angles from 14.79° to 2.93°, during which the asteroid ranged from 82,000 km to 29,000 km distance from the observer. A method is presented for obtaining photometrically filtered brightness values for the asteroid using unfiltered imaging techniques. Over 1,700 images of the asteroid produce a lightcurve with a peak‐to‐peak variation in V of 0.76 magnitude. Analysis of the lightcurve yields values for H = 30.86 ± 0.01 and G = 0.33 ± 0.03. Combined with other constraints on the kinetic energy and diameter of the asteroid, which suggest a low 1.8 g cm−3 density and albedo 0.05 ± 0.01, the value of H implies an asteroid of about 4.1 m in diameter, 28 m3 in volume, and 51,000 kg in mass. The determined value of G is out of range for normal, larger asteroids of albedo 0.05–0.15.
Abstract- A calibrated lightcurve is presented of the near-Earth asteroid 2008 TC sub(3), obtained before it impacted Earth on October 7, 2008. The asteroid was observed in unfiltered images from the ...end of astronomical twilight until the object entered Earth's shadow about 2h later. The observations covered a wide range of phase angles from 14.79 degree to 2.93 degree , during which the asteroid ranged from 82,000km to 29,000km distance from the observer. A method is presented for obtaining photometrically filtered brightness values for the asteroid using unfiltered imaging techniques. Over 1,700 images of the asteroid produce a lightcurve with a peak-to-peak variation in V of 0.76 magnitude. Analysis of the lightcurve yields values for H=30.86 plus or minus 0.01 and G=0.33 plus or minus 0.03. Combined with other constraints on the kinetic energy and diameter of the asteroid, which suggest a low 1.8gcm super(-3) density and albedo 0.05 plus or minus 0.01, the value of H implies an asteroid of about 4.1m in diameter, 28m super(3) in volume, and 51,000kg in mass. The determined value of G is out of range for normal, larger asteroids of albedo 0.05-0.15.
Abstract–
A calibrated lightcurve is presented of the near‐Earth asteroid 2008 TC
3
, obtained before it impacted Earth on October 7, 2008. The asteroid was observed in unfiltered images from the end ...of astronomical twilight until the object entered Earth’s shadow about 2 h later. The observations covered a wide range of phase angles from 14.79° to 2.93°, during which the asteroid ranged from 82,000 km to 29,000 km distance from the observer. A method is presented for obtaining photometrically filtered brightness values for the asteroid using unfiltered imaging techniques. Over 1,700 images of the asteroid produce a lightcurve with a peak‐to‐peak variation in
V
of 0.76 magnitude. Analysis of the lightcurve yields values for
H
= 30.86 ± 0.01 and
G
= 0.33 ± 0.03. Combined with other constraints on the kinetic energy and diameter of the asteroid, which suggest a low 1.8 g cm
−3
density and albedo 0.05 ± 0.01, the value of
H
implies an asteroid of about 4.1 m in diameter, 28 m
3
in volume, and 51,000 kg in mass. The determined value of
G
is out of range for normal, larger asteroids of albedo 0.05–0.15.
The shape and rotation of asteroid 2008 TC 3 SCHEIRICH, Peter; ĎURECH, Josef; PRAVEC, Petr ...
Meteoritics & planetary science,
10/2010, Letnik:
45, Številka:
10-11
Journal Article
Recenzirano
Abstract–
On October 6, 2008, a small F‐class asteroid 2008 TC
3
was discovered by Catalina Sky Survey telescope, and exploded 20 hr later in the Earth’s atmosphere at 37 km altitude. We analyzed ...available photometric data taken from 6 October 21:10 to 7 October 01:46 UT, and created a numerical model of a shape and rotation state of the asteroid. The asteroid was in excited rotational state. We found two approximately mirror solutions of orientation of its angular momentum vector. Rotational and precession periods are 99.20 and 97.00 s (errors of the rotational period for the two solutions are 0.03 and 0.04 s; of the precession period are 0.05 s for both solutions). The volume of the convex model and the length of the longest axis of the dynamically equivalent, equal volume ellipsoid are
and
, where
p
V
is surface geometric albedo. Assuming a mean albedo value for F taxonomic class, 0.049 ± 0.010, the volume is (25 ± 10) m
3
and the longest axis is (6.7 ± 0.8) m. This volume of the convex model is an upper limit on a real volume of the asteroid, which may be less by up to 20% due to concavities.
Abstract- On October 6, 2008, a small F-class asteroid 2008 TC sub(3) was discovered by Catalina Sky Survey telescope, and exploded 20hr later in the Earth's atmosphere at 37km altitude. We analyzed ...available photometric data taken from 6 October 21:10 to 7 October 01:46UT, and created a numerical model of a shape and rotation state of the asteroid. The asteroid was in excited rotational state. We found two approximately mirror solutions of orientation of its angular momentum vector. Rotational and precession periods are 99.20 and 97.00s (errors of the rotational period for the two solutions are 0.03 and 0.04s; of the precession period are 0.05s for both solutions). The volume of the convex model and the length of the longest axis of the dynamically equivalent, equal volume ellipsoid are and , where p sub(V) is surface geometric albedo. Assuming a mean albedo value for F taxonomic class, 0.049 plus or minus 0.010, the volume is (25 plus or minus 10)m super(3) and the longest axis is (6.7 plus or minus 0.8)m. This volume of the convex model is an upper limit on a real volume of the asteroid, which may be less by up to 20% due to concavities.
The NASA Double Asteroid Redirection Test (DART) spacecraft successfully impacted the Didymos-Dimorphos binary asteroid system on 2022 September 26 UTC. We provide an update to its pre-impact mutual ...orbit and estimate the post-impact physical and orbital parameters, derived using ground-based photometric observations taken from July 2022 to February 2023. We found that the total change of the orbital period was \(-33.240 \pm 0.072\) min. (all uncertainties are 3\(\sigma\)). We obtained the eccentricity of the post-impact orbit to be \(0.028 \pm 0.016\) and the apsidal precession rate of \(7.3 \pm 2.0\) deg./day from the impact to 2022 December 2. The data taken later in December to February suggest that the eccentricity dropped close to zero or the orbit became chaotic approximately 70 days after the impact. Most of the period change took place immediately after the impact but in a few weeks following the impact it was followed by additional change of \(-27^{+19}_{-58}\) seconds or \(-19 \pm 18\) seconds (the two values depend on the approach we used to describe the evolution of the orbital period after the impact -- an exponentially decreasing angular acceleration or an assumption of a constant orbital period, which changed abruptly some time after the impact, respectively). We estimate the pre-impact Dimorphos-Didymos size ratio was \(0.223 \pm 0.012\) and the post-impact is \(0.202 \pm 0.018\), which indicates a marginally significant reduction of Dimorphos' volume by (\(9 \pm 9) \%\) as the result of the impact.
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