The Case for Probe-class NASA Astrophysics Missions

Astrophysics spans an enormous range of questions on scales from individual planets to the entire cosmos. To address the richness of 21st century astrophysics requires a corresponding richness of telescopes spanning all bands and all messengers. Much scientific benefit comes from having the multi-wavelength capability available at the same time. Most of these bands,or measurement sensitivities, require space-based missions. Historically, NASA has addressed this need for breadth with a small number of flagship-class missions and a larger number of Explorer missions. While the Explorer program continues to flourish, there is a large gap between Explorers and strategic missions. A fortunate combination of new astrophysics technologies with new, high capacity, low dollar-per-kg to orbit launchers, and new satellite buses allow for cheaper missions with capabilities approaching strategic mission levels. NASA has recognized these developments by calling for Probe-class mission ideas for mission studies, spanning most of the electromagnetic spectrum from GeV gamma-rays to the far infrared, and the new messengers of neutrinos and ultra-high energy cosmic rays. The key insight from the Probes exercise is that order-of-magnitude advances in science performance metrics are possible across the board for initial total cost estimates in the range 500M-1B dollars

The Habitable Exoplanet Observatory (HabEx) Mission Concept Study Final Report

The Habitable Exoplanet Observatory, or HabEx, has been designed to be the Great Observatory of the 2030s. For the first time in human history, technologies have matured sufficiently to enable an affordable space-based telescope mission capable of discovering and characterizing Earthlike planets orbiting nearby bright sunlike stars in order to search for signs of habitability and biosignatures. Such a mission can also be equipped with instrumentation that will enable broad and exciting general astrophysics and planetary science not possible from current or planned facilities. HabEx is a space telescope with unique imaging and multi-object spectroscopic capabilities at wavelengths ranging from ultraviolet (UV) to near-IR. These capabilities allow for a broad suite of compelling science that cuts across the entire NASA astrophysics portfolio. HabEx has three primary science goals: (1) Seek out nearby worlds and explore their habitability; (2) Map out nearby planetary systems and understand the diversity of the worlds they contain; (3) Enable new explorations of astrophysical systems from our own solar system to external galaxies by extending our reach in the UV through near-IR. This Great Observatory science will be selected through a competed GO program, and will account for about 50% of the HabEx primary mission. The preferred HabEx architecture is a 4m, monolithic, off-axis telescope that is diffraction-limited at 0.4 microns and is in an L2 orbit. HabEx employs two starlight suppression systems: a coronagraph and a starshade, each with their own dedicated instrument

The Habitable Exoplanet Observatory (HabEx) Mission Concept Study Final Report

The Habitable Exoplanet Observatory, or HabEx, has been designed to be the Great Observatory of the 2030s. For the first time in human history, technologies have matured sufficiently to enable an affordable space-based telescope mission capable of discovering and characterizing Earthlike planets orbiting nearby bright sunlike stars in order to search for signs of habitability and biosignatures. Such a mission can also be equipped with instrumentation that will enable broad and exciting general astrophysics and planetary science not possible from current or planned facilities. HabEx is a space telescope with unique imaging and multi-object spectroscopic capabilities at wavelengths ranging from ultraviolet (UV) to near-IR. These capabilities allow for a broad suite of compelling science that cuts across the entire NASA astrophysics portfolio. HabEx has three primary science goals: (1) Seek out nearby worlds and explore their habitability; (2) Map out nearby planetary systems and understand the diversity of the worlds they contain; (3) Enable new explorations of astrophysical systems from our own solar system to external galaxies by extending our reach in the UV through near-IR. This Great Observatory science will be selected through a competed GO program, and will account for about 50% of the HabEx primary mission. The preferred HabEx architecture is a 4m, monolithic, off-axis telescope that is diffraction-limited at 0.4 microns and is in an L2 orbit. HabEx employs two starlight suppression systems: a coronagraph and a starshade, each with their own dedicated instrument.Comment: Full report: 498 pages. Executive Summary: 14 pages. More information about HabEx can be found here: https://www.jpl.nasa.gov/habex

Macrocyclic helicates: complexes of a 34-membered Schiff-base ligand

A unique double helical macrocyclic configuration of a new 34-membered Schiff-base macrocycle results from convergence of its two pyridine-2,6-diyldiimine units for meridional coordination of divalent metal ions; X-ray structure analysis establishes the cobalt(), nickel() and zinc() complexes as the first structurally characterised macrocyclic helicates

Zinc(II) complexes of putative obligate tetrahedrally co-ordinating pro-ligands

An attempt to impose tetrahedral geometry on zinc() through use of bis(salicylideneamino)biphenyl pro-ligands has produced hydrolytically sensitive complexes. The single-crystal structures of ZnL(EtOH)HL = 6{,}6prime or minute]-dimethyl-2,2prime or minute-bis(salicylideneamino)biphenylmonoclinic{,} space group 2/{,} = 11.654(2){,} = 11.753(2){,} = 18.878(3)A{,} small beta= 98.97(2)degree{,} = 4 and its pro-ligand HL monoclinic{,} space group 2/{,} = 13.911(2){,} = 13.759(2){,} = 12.015(2)A{,} small beta= 94.836(10)degree{,} = 4 have been determined. The co-ordination geometry at zinc is slightly distorted trigonal bipyramidal

Template synthesis of helicates of a [2 + 2] tetraimine macrocycle: crystal structure of the lead(II) perchlorate complex

The Schiff-base condensation of ,prime or minute-bis(2-aminophenoxy)--xylene and pyridine-2{,}6-dicarbaldehyde produced mononuclear complexes of the same 2 + 2 cyclocondensation product L in the presence of divalent metal ions ranging in size from Mn to Ba. The origin of the apparent insensitivity of the synthesis to the metal-ion size lies in the ability of the resulting 34-membered macrocycle to adopt either of two distinct co-ordination modes featuring double helical configurations stabilised by intramolecular small pi-small pi interactions. The crystal structure of PbLClOmiddle dot4MeCN trigonal{,} space group 3 with combining macron]1, == 20.557(3), = 23.843(3)A, = 0.0499, prime or minute= 0.0440 shows the metal ion co-ordinated by the NO donor set of the macrocycle within a fulldouble helical ligand array stabilised by five separate aromatic small pi-small pi interactions. Proton NMR studies of the diamagnetic complexes of L{,} assisted by detailed assignments of aromatic subspectra{,} provided evidence for retention of molecular helicity in solution; an interesting example of -spin decoupling of Pb is noted in the field-dependent spectra of PbLClO in CDCN