Is NASA covering up Hubble pictures?

From the Hubble Space Telescope "Call for Observing Proposal" manual:

"The telescope does not generally observe targets within 50 degrees of the Sun [...]. When the scientific justification is compelling, time critical observations of solar-system objects lying between 45 and 50 degrees from the Sun may be carried out."

Keeping this limitations in mind, here is a chronology of the HST observations:

Some images obtained in September and October 1995 (cf below).
The comet was in the forbidden 50 degree region from early November 1995 until early March 1996
In March 1996, all the available observing time was focused on Comet Hyakutake
HST performed some observations in April, May, June, July, September, October (the observing log is available).
- The April--June images looked the same as those of fall 1995, so there was no urgency to process/release them.
- The comet started to develop some nice jets in July 1996
- Most of the comet scientist were preparing and attending scientific meetings in Europe during the summer.
- In response to enquiries in October (at the time of the American Astronomical Society Division for Planetary Science meeting), H.Weaver (P.I. of the HST program) processed some of the latest images an put them on the Web; they are also shown below.
Late October 96: the comet enters again the 50deg. exclusion limit. It will not leave it until August 1997. In March 1997, the comet will be at 46 deg from the Sun, and therefore may theoretically be observed. However, the second HST servicing mission is scheduled for February 1997, and it is unlikely that the telescope will be ready in time to observe Hale Bopp.

There were also many questions about the 1 year proprietary period on HST data. The Principal Investigator (P.I.) and his team have proposed a project to the Space Telescope Science Institute (ST-ScI). Such a proposal represents lots of time and efforts. If the proposal is among the bests of all those that are received by the ST-Sci, that project is awarded some observing time, and the PI must send a "Phase II" proposal, which describes the observations in a VERY detailed way. This represents a HUGE amount of work. When the observations are finally performed, the P.I. receives the data at his institute. To transform these raw data into nice images is time consuming. To measure them and analyze them scientifically can take many months. The one year proprietary period ensures that the team who has done all the work has a privileged access to the data, but that year is very short in comparison to the amount of work that has to be done. On the other hand, if the data contain something spectacular, the P.I. can decide to produce quickly some nice-looking images and release them to the public. These are widely available, but should not be confused with the real data, which are usually not as pretty, but scientifically much more interesting for the astronomers (and most probably boring for anybody else).

Copy of H.Weaver's page:

The above figure shows the temporal evolution of Comet Hale-Bopp over the course of about 1 year, as observed by the Hubble Space Telescope. In the far-left frame we caught the comet about 60 hours after a huge outburst of dust, and the image shows an impressive spiral structure reminiscent of a water sprinkler observed from above. The middle frame shows the comet during a more quiescent phase in which hardly any structure is seen in the coma without employing a strong intensity contrast in the display. The image at the far-right shows that the comet has now taken on a "porcupine" appearance as at least five jets can be seen sprouting from the nucleus. The nucleus of the comet is located at the center of each frame, but most of the light observed is due to scattered sunlight from fine dust grains that are emitted from the nucleus and which produce the cometary "coma".

Each frame above is 10 arcsec across. For the far-left frame this corresponds to 47,000 km at the comet, for the middle frame this corresponds to 49,000 km at the comet, and for the far-right frame this corresponds to 21,000 km at the comet. (The comet was much closer to the Earth during the September 1996 observations.)

Olivier Hainaut

Created: Thu Nov 28 16:53:34 1996 --- Updated: Sat Dec 14 21:15:00 1996 -- Hits: