0 Assigned ID: 1733 ----- Attempting Submission 1 (Fri Mar 01 20:25:36 GMT 2013) ----- HST Phase I Proposal 1733 (lutetia_hst2013_03_01.aptbackup.apt.2013_03_01_16_30.aptbackup) successfully submitted. 0 ----- Attempting Submission 1 (Tue Jun 25 20:04:36 GMT 2013) ----- (21) Lutetia is one of the largest asteroids in the main belt, with dimensions of 121x101x75 km along its principal axes of inertia. On July 10, 2010, the European Space Agency's Rosetta spacecraft passed within 3168 +/- 7.5 km of Lutetia's surface. However, even after the Rosetta flyby, fundamental uncertainties remain about the composition of Lutetia's surface. The primary reason for this is that from visible to millimeter wavelengths, Lutetia's reflectance spectrum is almost completely devoid of absorption features and contains nothing that can uniquely constrain its surface composition. The scientific literature is now split with about half advocating an enstatite chondrite composition and half a carbonaceous chondrite composition. Although these materials look similar in the visible/IR, they have markedly different appearances in the NUV. In addition, the FUV spectrograph on the Rosetta spacecraft identified a strong absorption edge in Lutetia's spectrum at 170nm. This could be indicative of plagioclase feldspar minerals or water ice. The presence of either of these materials is not expected on Lutetia's surface and would be a major discovery. However, it is not possible to confirm/rule out their presence using existing data--for that NUV spectra are required. We propose a focused, 4-orbit program to obtain the spectrum of Lutetia from 180-570nm using STIS/G230L and STIS/G430L. The goal of this program is to obtain spectra of the asteroid (21) Lutetia from 180-570nm. Using our best estimate of Lutetia's spectrum--derived from FUV spectra by the Rosetta Alice spectrograph and ACS photometry--and the STIS and COS ETCs, we find that the STIS/G230L is more efficient than the COS/G230L. The predicted global count rate from the STIS ETC is 2460, well below the MAMA bright object limits. We will therefore operate the STIS NUV MAMA in TIME-TAG mode with a very conservative buffer time of 650s. Seen from Earth at opposition, Lutetia is about 0.075" in diameter, so it will appear only marginally larger than a point source. Thus, we will use the 52"x0.2" slit. Based on the results from the ETC, obtaining a SNR of 10 at 200 nm for a 2-pixel resel (3.2 A resolution) requires 7331s of integration time. In this phase II proposal, we obtain a total of 7830s. SNRs in excess of 100 will be achieved at wavelengths greater than ~260 nm. The STIS/G430L configuration provides a bridge between the NUV and visible, covering the wavelength range of 295-570 nm with high SNR. Since the Sun, and hence Lutetia, is significantly brighter in the visible than the NUV, we can obtain comparable SNRs in just 200s of total integration time using the STIS CCD and G430L grating (CR-SPLIT=3). The SNR is > 50 for all wavelengths > 310 nm. The length of the planned orbits (and amount of unused observing time, if any) should be re-checked in early 2014, when the orbit of HST becomes known. SOLAR SYSTEM 12 false true 0.0 0.0 false false false SUPPORTED SOLAR SYSTEM ASTEROID The asteroid (21) Lutetia TYPE=ASTEROID,A=2.434254224700,E=0.164545157839,I=3.063861842541,O=80.884245472306,W=250.213284373741,M=220.967267326744,EQUINOX=J2000,EPOCH=22-MAR-2014:00:00:00,EpochTimeScale=UTC EARTH STIS/NUV-MAMA Spectroscopic No No G230L 2376 STIS/CCD Spectroscopic No No G430L 4300 1372190070627 /private/var/folders/_w/s20kp9948xlbz0008k8xg2h00000gp/T/OPVisit4107295297193300320.xml The scheduling data was generated by CASM 21.2. CASM was run in Phase II mode. For accurate determination of Lutetia's geometric albedo (defined as the reflectance at a phase angle of 0 deg) we require the phase angle correction to be < 30%. This constrains the observations to occur when Lutetia's phase angle is < 2.7 deg, when seen from Earth, which occurs between 2014 Mar 17-28. Although we can accept observations at any time during this window, we strongly prefer the visit be made as close to opposition (2014-Mar-22 11:00:00) as possible. 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