The origins of the martian moons Phobos and Deimos remain enigmatic. Over the past decades a range of spacecraft have observed Phobos and Deimos in order to constrain their origin and evolutionary history, with proposals for their origins ranging from captured asteroids, to coalesced material from a giant impact on Mars. However, given the orbits these spacecraft and the orbits of Phobos and Deimos, Phobos has garnered the majority of the attention. Now thanks to the unique orbit of the Emirates Mars Mission (EMM) Hope spacecraft and a minor correction to its nominal science orbit, EMM has a unique opportunity to examine Deimos in great detail while fully retaining the originally designed mission to capture the variability in the martian atmosphere and exosphere.Following a minor orbital adjustment maneuver campaign beginning in August 2022, EMM will encounter Deimos multiple times, progressively observing the martian moon at lower and lower distances beginning in early 2023. These flybys culminate in the closest approach of ~150 km, observing the mostly illuminated, far side of Deimos. All three EMM instruments, the Emirates eXploration Imager (EXI), the Emirates Mars Infrared Spectrometer (EMIRS), and the Emirates Ultraviolet Spectrometer (EMUS) have observation sequences tailored to these flybys, collecting the highest resolution multispectral visible imaging data, thermal infrared surface temperatures and emission spectra, and ultraviolet spectra. When combined these instrument observations will provide key insights into the composition, morphology, and surface physical properties of the least studied martian moon, Deimos.

We present a New Frontiers class mission concept of a Jupiter system observatory, located at the Sun-Jupiter Lagrangian point L1 focused on time-domain sciences, including the weather systems and deep interior structure of Jupiter, ionosphere-magnetosphere-solar wind coupling, activities of Galilean moons, and impact flashes on Jupiter.This concept also brings unique advantages to study jovian irregular satellites, upstream solar wind, interplanetary/interstellar dust populations, and other minor bodies that are critical to understand the current and past interactions between the jovian system and the solar system that cannot be achieved otherwise.The conceptual observatory will provide high synergistic values to current and future missions with broad scientific implications regarding solar system evolution, exoplanets, and astrophysics studies, and could serve as a strategic facility for the planetary science and exploration in the coming decade.

The Harvest Oil Platform, near Point Conception, California, has long served as the NASA prime verification site for the TOPEX/POSEIDON and Jason series of reference altimeter missions. In this brief review article, we provide a short history of the platform verification experiment dating to the site selection in 1989. We describe the evolution of the verification data record over the past three decades, and demonstrate how the results have informed the development of a stable and accurate climate data record of sea level change from satellite altimetry.

The work described in this paper harnesses an open-source astrodynamics engine and visualization to quantify the performance of on-board optical navigation. It introduces the Hough Circles transform as a candidate method for centroid and apparent diameter extraction. The coupled nature of the simulation enables simultaneous pointing and orbit determination with dynamic image generation, all in a realistic flight-software environment. Navigation is done about Mars solely using optical images, and by means of limb or centroid/diameter extraction. Through the implementation of pre-existing algorithms for a baseline comparison and the development of Hough Circles, an end-to-end autonomous flight-software stack is developed and tested. This research provides insight into achievable navigation accuracy and image processing methods, as well as outlier mitigation for mission readiness.

On July 4, 2005 at 05:44:34 UTC the Impactor spacecraft (s/c) impacted comet 9P/Tempel 1 with a relative speed of more than 10 km/s. The Flyby s/c captured the impact event, using both the medium resolution imager and the high resolution imager, and tracked the impact site for the entire observing period following impact. The objective of the Impactor s/c was to impact in an illuminated area viewable from the Flyby s/c and telemeter high-resolution context images of the impact site prior to impact. The Flyby s/c had two primary objectives: (1) capture the impact event in order to observe the ejecta plume expansion dynamics and (2) track the impact site for at least 800 s to observe the crater formation and capture high-resolution images of the fully developed crater. All of these objectives were met by estimating the trajectory of each spacecraft relative to 9P/Tempel I using the autonomous navigation system, precise attitude information from the attitude determination and control subsystem, and allowing each spacecraft to independently select the same impact site. This paper describes the challenges of targeting and tracking comet 9P/Tempel 1. (c) 2007 Wiley Periodicals, Inc.

On July 4, 2005 at 05:44:34.2 UTC the Impactor Spacecraft (s/c) impacted comet Tempel 1 with a relative speed of 10.3 km/s capturing high-resolution images of the surface of the nucleus just seconds before impact. Meanwhile, the Flyby s/c captured the impact event using both the Medium Resolution Imager (MRI) and the High Resolution Imager (HRI) and tracked the nucleus for the entire 800 sec period between impact and shield attitude transition. The objective of the Impactor s/c was to impact in an illuminated area viewable from the Flyby s/c and capture high-resolution context images of the impact site. This was accomplished by using autonomous navigation (AutoNav) algorithms and precise attitude information from the attitude determination and control subsystem (ADCS). The Flyby s/c had two primary objectives: 1) capture the impact event with the highest temporal resolution possible in order to observe the ejecta plume expansion dynamics; and 2) track the impact site for at least 800 sec to observe the crater formation and capture the highest resolution images possible of the fully developed crater. These two objectives were met by estimating the Flyby s/c trajectory relative to Tempel I using the same AutoNav algorithms along with precise attitude information from ADCS and independently selecting the best impact site. This paper describes the AutoNav system, what happened during the encounter with Tempel I and what could have happened.

The engineering goal of the Deep Impact mission is to impact comet Tempel 1 on July 4, 2005, with a 370 kg active Impactor spacecraft (s/c). The impact velocity will be just over 10 km/s and is expected to excavate a crater approximately 20m deep and 100m wide. The Impactor s/c will be delivered to the vicinity of Tempel 1 by the Flyby s/c, which is also the key observing platform for the event. Following Impactor release, the Flyby will change course to pass the nucleus at an altitude of 500 km and at the same time slow down in order to allow approximately 800s of observation of the impact event, ejecta plume expansion, and crater formation. Deep Impact will use the autonomous optical navigation (AutoNav) software system to guide the Impactor s/c to intercept the nucleus of Tempel 1 at a location that is illuminated and viewable from the Flyby. The Flyby s/c uses identical software to determine its comet-relative trajectory and provide the attitude determination and control system (ADCS) with the relative position information necessary to point the High Resolution Imager (HRI) and Medium Resolution Imager (MRI) instruments at the impact site during the encounter. This paper describes the Impactor s/c autonomous targeting design and the Flyby s/c autonomous tracking design, including image processing and navigation ( trajectory estimation and maneuver computation). We also discuss the analysis that led to the current design, the expected system performance as compared to the key mission requirements and the sensitivity to various s/c subsystems and Tempel 1 environmental factors.

The engineering goal of the Deep Impact mission is to impact comet Tempel I on July 4, 2005, with a 370 kg active Impactor spacecraft (s/c). The impact velocity will be just over 10 km/s and is expected to excavate a crater of approximately 20 m deep and 100 in wide. A second spacecraft, the Flyby s/c, is responsible for delivering the Impactor spacecraft and will perform a slowing maneuver, following Impactor release, to observe the impact event, ejecta plume expansion, and crater formation, which will take place over a period of approximately 800 seconds. The science objective is that of exposing the interior material and understanding the properties of the nucleus. Deep Impact will use the autonomous optical navigation (AutoNav) software system to guide the Impactor s/c to Tempel I intercept at a location that is illuminated, while the Flyby s/c uses identical software to determine its comet-relative trajectory in order to provide the attitude determination and control system (ADCS) with the relative position information necessary to point the High Resolution Imaging (HRI) and Medium Resolution Imaging (MRI) instruments at the impact site during encounter. There are two key science epochs that drive system performance during the encounter: 1) Time of impact (TOI) when impact event imaging occurs; and 2) Time of final crater imaging (TOFI) where the highest resolution images of the fully developed crater are obtained using the MRI and HRI instruments on the Flyby s/c. These two science epochs require both an impact in an illuminated area and good knowledge of the impact site. This paper describes the Impactor s/c autonomous targeting strategy including image processing and navigation (trajectory estimation and maneuver computation). Impactor s/c system performance is based on Monte Carlo analyses and MATLAB simulation, which allows for study of the targeting sensitivity to different image processing algorithms, nucleus topography, lighting conditions, and attitude determination and control system performance.

We present calibration results from Jason-1 (2002-) and TOPEX/Poseidon (1992-) overflights of dedicated verification sites on the Mediterranean island of Corsica and on a California offshore oil platform (Harvest). Harvest served for a decade (1992-2002) as a calibration site for the TOPEX/Poseidon (T/P) mission, and is serving in a similar capacity for Jason-1. Initiated in 1996, the Corsica experiment features a fiducial reference station near Aspretto, and a primary sub-satellite tide-gauge deployment site 40 km south at Cape Senetosa. Both Corsica and Harvest feature carefully designed collocations of space-geodetic and tide-gauge systems to support the absolute calibration of the altimetric sea-surface height (SSH). By incorporating improved estimates of the Jason-1 sea-state bias and columnar atmospheric wet path delay, we observe a bias of about 12 cm.

Calibration data for the TOPEX/Poseidon altimeter was collected at Texaco's Platform Harvest off the coast of southern California. The CU sea level system, containing two Paros depth sensors, was designed and installed at Platform Harvest to collect submerged pressure data. Corrections for instrument bias, water density, and atmospheric pressure were applied to each depth sensor and sea level obtained relative to an established benchmark on the platform. Estimates of H 1/3 were determined to characterize the sea state during the 2‐h period surrounding each overflight using classical theory. To test the validity of these assumptions, the ratio between spectra measurements from the upper and lower depth sensors was normalized by the expected theoretical ratio. The results differ from theory by ∼1% with a standard deviation of ∼2%. The weighted mean frequency as a function of H 1/3 was calculated during several overflight periods. Results indicate that the frequency content tends to be bimodal for H 1/3 values below 2.5 m.

On July 4, 2005, another first in space exploration was achieved. NASA's Deep Impact spacecraft (s/c) released a small, 350 kg Impactor s/c designed to target comet Tempel 1, estimated to be 14 km x 5 km x 5 km in size at the time of release. With a closing speed of approximately 10.3 km/s, the Impactor s/c autonomously guided itself to impact and captured 40 cm resolution images, the highest resolution images ever of the surface of a cometary nucleus, just moments before the collision. The objective of the Impactor s/c was to impact in an illuminated area viewable from the Flyby s/c. This paper describes the Impactor encounter sequence design, execution and contingency planning that contributed to the successful outcome in which all objectives were met.