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Results for “orbital eccentricity”

Search indexed NASA NTRS and DOE OSTI research on propulsion, heat transfer, battery materials and energy systems. Follow report and document links to the original sources.

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NASA NTRS2018

Do Close-in Giant Planets Orbiting Evolved Stars Prefer Eccentric Orbits?

The NASA Kepler and K2 Missions have recently revealed a population of transiting giant planets orbiting moderately evolved, low-luminosity red giant branch stars. Here, we present radial velocity (RV) measurements of three of these systems, revealing significantly non-zero orbital eccentricities in each case. Comparing these systems with the known planet population suggests that close-in giant planets around evolved stars tend to have more eccentric orbits than those around main sequence stars. We interpret this as tentative evidence that the orbits of these planets pass through a transient, moderately eccentric phase where they shrink faster than they circularize due to tides raised on evolved host stars. Additional RV measurements of currently known systems, along with new systems discovered by the recently launched NASA Transiting Exoplanet Survey Satellite (TESS) mission, may constrain the timescale and mass dependence of this process.

Thomas Barclay↗
NASA NTRS1979

Gravitational spectra from the tracking of planetary spacecraft in eccentric orbits

Two dimensional gravitational spectra are derived from simple harmonic analysis of range rate tracking data on planetary orbiters. The eccentricity of the orbit is arbitrary and results are shown to vary substantially with the aspect angle of the tracking line of sight with the orbit plane. The development for arbitrary start with stop times (with respect to periapsis) uses modified eccentricity functions evaluated by quadrature. Simulations with a point-masses model of Venus using tracking data on the Pioneer Venus Orbiter show excellent predictions of the average orbiter spectrum over one Venus day. The Venus gravitational signal should be above the tracking noise level for arc lengths longer than 40 deg (in true anomaly) about periapsis and for terms as high as 55th degree. analysis has been made of tracking residuals from a short arc fit to Mariner Mars 9 data over the Hellas Basin (using a complete 6th degree field). Results are most consistent with higher residual gravitational power than predicted from Kaula's rule for Mars.

Wagner, C. A.↗
NASA NTRS2019

Lunisolar Perturbations of High-Eccentricity Orbits Such as the Magnetospheric Multiscale Mission

For highly eccentric orbits such as that of the Magnetospheric Multiscale (MMS)mission, with apogee radius now 29.34 Earth radii, the third-body effects of Sun andMoon are the major perturbations. One key consequence is an oscillation in MMSperigee altitude, on an approximately 6 year cycle. This variation has already requiredperigee-raise maneuvers to avoid an untimely reentry. There is also a long-termevolution in the orientation of the MMS orbit, with period roughly twice as long. Thiseffect may potentially be useful for MMS science studies, as it can bring the spacecraftinto new regions of the magnetosphere.

Williams, Trevor↗
NASA NTRS1972

Ephemeris of a highly eccentric orbit - Explorer 28.

An ephemeris has been obtained for Explorer 28 (IMP 3) which agrees well with 2 years of radio observations and with SAO observations a year later. This ephemeris is generated over the 3 year lifetime by a numerical integration method utilizing a set of initial conditions at launch and without requiring further differential correction. Because highly eccentric orbits are difficult to compute with acceptable accuracy and because a long continuous arc has been obtained which compares with actual data to a known precision, this ephemeris may be used as a standard for computing highly eccentric orbits in the earth-moon system. Orbit improvement was used to obtain the initial conditions which generated the ephemeris. This improvement was based on correcting the energy by adjusting the semimajor axis to match computed times of perigee passage with the observed. This procedure may generate errors in semimajor axis to compensate for model errors in the energy; however, this compensation error is also implicit in orbit determination itself.

Lowrey, B. E.↗
NASA NTRS2020

TOI-677b: A Warm Jupiter (P=11.2 days) on an Eccentric Orbit Transiting a Late F-type Star

We report the discovery of TOI-677b,first identified as a candidate in light curves obtained within Sectors 9 and 10 of the Transiting Exoplanet Survey Satellite(TESS)mission and confirmed with radial velocities. TOI-677b has a mass of M(p) = 1.236(+0.069,- 0.067) M(J), a radius of R(P)=1.170 ± 0.03 R(J), and orbits its bright host star (V = 9.8 mag) with an orbital period of 11.23660 ± 0.00011 d, on an eccentric orbit with e = 0.435 ± 0.024. The host star has a mass of M(*) = 1.181 ± 0.058 M(ʘ), a radius of R(*)= 1.28(+0.03,-0.03) R(ʘ), an age of 2.92 (+0.80,-0.73) Gyr and solar metallicity, properties consistent with a main-sequence late-F star with T(eff)=6295 ± 77K. We find evidence in the radial velocity measurements of a secondary long-term signal, which could be due to an outer companion. The TOI-677 b system is a well-suited target for Rossiter–Mclaughlin observations that can constrain migration mechanisms of close-in giant planets.

Andrés Jordán↗