How A/CC broke the 2002 NT7 story

By Bill Allen,   A/CC editor & links librarian

Next essay: "The pursuit of 2003 CR20"
Updated: 29 March 2003 — New: 26 July 2002

The Asteroid/Comet Connection isn't particularly concerned with the theory and politics of impact hazards and planetary defense. You will find little in our pages about the lore and history of Earth impacts. A/CC's mission is to present information about minor objects as represents their developing science and exploration, and their future development. That is, as constructive rather than destructive elements in humankind's spacefaring future. It happens that two of the most active sources for useful and linkable information about minor objects are the JPL NEO Program and NEODyS impact risk pages, so we "monitor the monitors," and that's how we came to notice that an unusual new asteroid was getting special attention.

The big story about the asteroid 2002 NT7, according to the piece's original time stamp, first began to go public ten minutes before midnight in London on 23 July, when the headline, Space rock 'on collision course' appeared on BBC News Online. It, and a version stamped 3-1/2 hours later, got several details wrong, but it put the essential point right: An asteroid discovered just weeks ago has become the most threatening object yet detected in space. A preliminary orbit suggests that 2002 NT7 is on an impact course with Earth on 1 February 2019.

Dr. Benny Peiser, who is quoted in the BBC piece, earlier that day led the 23 July edition of his Cambridge Conference Correspondence with a full quote of the Asteroid/Comet Connection (A/CC) Monday evening 2002 NT7 news summation:

It took until early evening Monday at NEODyS in Italy to update their impactor table for 2002 NT7 with 13 new observations from Sunday night. And no wonder. With this they have placed NT7's February 1st, 2019 "virtual impactor" at a first-ever positive Palermo Scale rating of 0.18, up from yesterday's -0.11, which had been an easing from Saturday's -0.04. They and JPL, however, still have the 2019 impactor Torino Scale rating at 1.

JPL's NEO Program site this morning posted a new risk assessment for NT7, giving it a Palermo Scale rating of -0.05 cumulatively, while specifically rating the 2019 event at -0.10. Later in the day these ratings were revised to -0.15 for the 2019 event (better), although the cumulative rating that incorporates other later possible events, especially one in 2035, is now -0.02 (worse).

Sunday night's work includes nine observations from Siding Spring in Australia, which figured prominently in Near-Earth Object (NEO) searches until the government there cut funding.

Since 18 July, NEODyS and JPL have had NT7 at Torino Scale 1 ("merits special monitoring"). This is a large object with a diameter estimated at more than 2 km. (1.4 miles). It has a 42°-inclined orbit that crosses the orbit of Mars and barely crosses the orbit of Earth. It approaches Earth most closely from south of the ecliptic, where there is little PHO surveillance, and that, along with NT7's inclination, may be part of why it hasn't been spotted until now.

As pointed out to A/CC by Jon Giorgini, JPL's lead scientist on studying 29075 1950 DA, that asteroid on 4 April 2002 actually became the first ever to get a positive Palermo Scale rating. This rating was, and remains in effect, for a possible event on 16 March 2880, 35 generations from now. However, the NEODyS and JPL NEO Program risk monitoring efforts and their Web sites only concern themselves with potential hazards over the next hundred years or so.

To readers who regularly follow the A/CC News page, the 2002 NT7 story had been developing for the whole previous week.

NT7 was discovered on 9 July by MIT's LINEAR program, and first came to A/CC's attention when the Minor Planet Center (MPC) posted MPEC 2002-N38 on 14 July with early observations. As A/CC News reported at the time, within a day both JPL and NEODyS had added NT7 to their risk pages at Torino Scale 0. So far this was all routine, just another freshly discovered asteroid moving through the NEO surveillance system that involves MPC, NEODyS, JPL, and the various observatories, including many "amateurs" whose expert nightly volunteer work is critical to the process of refining orbits to where it becomes known each object is not a forseeable hazard.

On Thursday we noticed that NEODyS had raised NT7 to Torino Scale 1 and posted this lead news item: On 18 July JPL is showing 43 possible impact solutions from 2010 to 2099, all at Torino Scale 0 based on 43 observations, according (at 16:21 UT) to its page with a 15 July date. NEODyS has 30 solutions from 2019 to 2080, and nine are at Torino Scale 1, based on 50 observations. Later in the day JPL also elevated NT7 to Torino Scale 1.

At 2:57pm Mountain Time (20:57 UT), A/CC News posted that, NEODyS today, 20 July, has a February 1st, 2019 virtual impactor for 2002 NT7 rated at Palermo Scale -0.04, which borders on calling an unprecedented technical review by the International Astronomical Union. However, this is based on only 63 observations from 11 days, and further data is likely to ease concern.

The JPL NEO Program did not update its NT7 assessment from sometime Friday until Sunday afternoon, when A/CC News reported that, NEODyS today, 21 July, has a February 1st, 2019 virtual impactor for 2002 NT7 rated at Palermo Scale -0.11. That's an easing from yesterday's -0.04, however JPL's new rating this afternoon is -0.09 cumulatively, and -0.21 specifically for the 2019 event. That is the opposite of easing from JPL's last ratings two days ago at -0.27 cumulative and -0.95 specific. These NEODyS and JPL ratings are based on 83 observations from 12 days (20 were added overnight), and time and further data is likely to bring better news.

It was the last of our reports of the next day, Monday, reproduced in full at the top of this page, that led to the world news media picking up on 2002 NT7's looming danger.

One certainly hopes this story will soon disappear and 2002 NT7 becomes just another among a handfull of briefly famous but otherwise obscure objects with orbits that eventually calculated to miss Earth for as far into the future as today's detection methods and computer software can predict. Many experts will now weigh in about the possibilities and probabilities, and what if anything to do about it all. But the uproar started quietly on a Summer Saturday afternoon in Santa Fe, New Mexico as A/CC News routinely observed the routine work of NEO orbit dynamicists in Pisa, Italy and Pasadena, California.

Everything thing below here was added on 22 August 2002, including the news coverage that had been on the A/CC News page, plus new information, corrections, commentary, and a collection of news links.

A/CC's Further NT7 News Coverage

On Monday July 22nd, NEODyS posted a 0.18 Palermo Scale (PS) rating for a possible 1 February 2019 Earth impact event. This was a historic first-ever rating on the positive side of that scale made public for a possible event within current lifetimes. The somewhat outmoded (see Milani et al.) but still standing International Astronomical Union policy of December 2001 calls for a consensus-of-experts' statement to be prepared following a voluntary submission to a technical review before a positive Palermo Scale rating is made public. However, under these particular circumstances, and in a changing PHO research environment, apparently it was decided that no formal IAU statement was needed. (The public record has yet to be set straight as to whether a formal or informal technical review was actually held.)

In hindsight, it would have been far better for the media to have had a prepared IAU statement to work from. As it happened, once the BBC and CBS had published reports, writers and editors at countless news organizations worldwide were left alone to sort out for themselves what this story was about, and how much importance to give it. Almost all of their reports tried in regular professional fashion to include the proper caveats and good quotes from NASA personalities and other experts. The result was to find themselves collectively castigated by NASA and a legion of NEO observers who hadn't invited, weren't prepared for, and didn't want media interest in 2002 NT7 and its hazard rating.

The truth is that the main news point was wrong. The NEO community milestone that touched it all off was predictably fleeting, and it certainly was at a stage much too early to raise public concern. To cap it all off, NT7's calculated risk went to zero in less than a week after the story broke, a rapidity that was pure happenstance, as opposed, say, to a 2002 CU11 or MN.

The 2002 NT7 positive Palermo Scale rating of 22 July was based on only a very few days' observations, and thus was quite preliminary and could be expected to change for the better with more time and observations. That said, this PS rating, when it rolled over into positive numbers, did at that moment show that the possibility of a known object hitting Earth within present lifetimes was slightly more likely than the random chance of an unknown object hitting any time without warning (the "background risk"). It was a first, and NT7's PS rating would actually go higher before it fell.

NEODyS and JPL had had NT7 on their pages since soon after its announcement by the Minor Planet Center on 14 July, and they both raised it to Torino Scale 1 ("merits special monitoring") on 18 July. This is a large object with a diameter estimated at more than 2 km. (1.4 miles). It has a 42°-inclined orbit that crosses the orbit of Mars and barely crosses the orbit of Earth. It approaches Earth most closely from south of the ecliptic, where there is little PHO surveillance, and that, along with NT7's inclination, may be part of why it hasn't been spotted until now.

Although the report currently linked has a later time stamp, the BBC online science news item about 2002 NT7 posted at midnight of the 23rd in England was the first that the mainstream news media and regular space/astronomy media picked up on this story, which had been developing since early the previous week. The 25 and 26 July editions of Cambridge Conference Correspondence carry a large selection of complete news texts from various news outlets, plus criticism by experts about this reporting, and some silly stuff, too. And there is plenty more of all of that in daily CCC editions for 27-29 July.

There was an interruption in the flow of observations for several days, reported by A/CC at the time and noted later by Sky & Telescopecookies required as odd, but viewing was made difficult by the full Moon. Then work by a few observatories around the world resulted in removing the 2019 impactor entirely by first NEODyS and then JPL during 28-29 July. One last impact solution, for the year 2060, took until August 1st to eliminate, after which 2002 NT7 left the risk pages entirely.

To get an idea of why it is to be expected that risk ratings for 2002 NT7 and any other new-found object can, and are likely to, change so much in just a month, see an advisory posted here on 30 July from Jon Giorgini of JPL's Solar System Dynamics Group.

Until early 2003, we weren't able to fill in the biggest gap still remaining in the 2002 NT7 story, something that months later still hadn't been explained or talked about: Whether a formal or informal technical review was actually held as 2002 NT7's Palermo Scale rating climbed toward and went past 0.0. If there was some kind of review, who was involved and with what outcome? And has there been, or will there be, a review of whatever process led to a decision not to prepare an official statement that the news media could have used for guidance, once it found out that astronomers had something interesting in their scopes?

When A/CC public raised the issue again in March 2003, mentioning that David Morrison had declined to respond to A/CC's inquiry, Benny Peiser in his Cambridge Conference Correspondence edition of 12 March reported that he, too, had inquired, and received this response in August 2002 from Dr. Morrison:

Asteroid 2002 NT7 appeared on the Risk Pages of both NEODyS and JPL starting July 18 [sic]. On July 22 the Pisa site raised the issue of a possible IAU Technical Review, given the Palermo Technical Scale value. However, they argued that such a review was not necessary, since (1) both the Pisa software robots (CLOMON and CLOMON2) and the JPL one (Sentry) were providing automatic, frequently updated confirmation, (2) the value of the Palermo Technical Scale was near but not much over the nominal threshold for such a review, and (3) the asteroid was easily observable, with new data coming in nearly every day. The same day (July 22), I, as Chair of the IAU WGNEO, wrote back that "The argument for not initiating an IAU technical review for 2002 NT7 seems sound to me", and noting that the Technical Review was voluntary in any case. Thus no IAU Technical Review was held, and there was no interruption in the steady refinement of the orbit of 2002 NT7, for which (as I understand it) the risk of impact in 2019 was reduced to essentially zero on July 26, and the other possible risks at later dates were eliminated by August 1. Meanwhile the inaccurate and even fallaceous scare statements concerning 2002 NT7 had begun appearing in the British Press on July 24, and you know the course of this story since."

To get a look at the subject of all this verbiage, see Klet Observatory's 504Kb GIF animation of six 19 July images showing 2002 NT7's motion, and a stack of 29 July images by Linz Observatory in Austria (NT7 is the faint object at center without a trail). It was Linz's observations early on the 28th — the first in three and a half days — that led to the 2019 possible impact solution being removed. For some more observing details, and another dose of scathing commentary on the media, see the Camarillo Observatory's 9 August news release.

NT7 News Updates

Clarifications & corrections in A/CC's reporting

Thanks to the people who sent pointers and corrections to A/CC about its 2002 NT7 reporting. We try to get things straight, so we like to be corrected on anything from factual problems down to smaller housekeeping items such as bad links or syntax accidents.

One: On 22 July, A/CC reported that 2002 NT7 had the first instance of a positive Palermo Scale rating made public. In fact, the distinction for the very first positive Palermo Scale rating goes to an announcement made on 4 April 2002 for a possible event on 16 March 2880 (35 generations from now) involving 29075 1950 DA. This was brought immediately to A/CC's attention by Jon Giorgini of JPL, who led the team that made that determination, and A/CC's reporting was updated accordingly.

Two: Prior to the 22 July milestone, A/CC had reported that the growing Palermo Scale ratings at JPL and NEODyS for 2002 NT7 bordered "on calling an unprecedented technical review by the International Astronomical Union." Actually, there have been previous technical reviews, with the most recent being for 2000 SG344 in November 2000 (which set off an uproar on a par with the 2002 NT7 ruckus). However, those proceedings came before the Palermo Scale was put into IAU policy to trip at a rating of 0.0, which was what A/CC was anticipating in its reporting.

Three: On the 1st of August, both NEODyS and JPL pulled 2002 NT7 from their risk pages, where it had been during 14-31 July, declaring that all "virtual impact" possibilities appear to have been eliminated, including the last concern about a possible event in 2060. Actually, NEODyS signalled this change through its Valladolid sister site in Spain, while the main site in Pisa, Italy was down due to a power outage and ensuing problems.

When the Pisa Web site was brought back up on the 2nd, it briefly retained the NT7 assessment from the 31st, which A/CC noticed and reported as a possibly spurious result from the NEODyS CLOMON system. A/CC has since learned from Genny Sansaturio, who maintains both NEODyS sites, that the actual problem was in the supporting infrastructure and not in the CLOMON orbital dynamics software.

Some of the Headlines

And, from the scientists:
  • NASA/JPL NEO Program home page on 24 July: "Asteroid 2002 NT7":
    Asteroid 2002 NT7 currently heads the list on our IMPACT RISKS Page because of a low-probability Earth impact prediction for February 1, 2019. While this prediction is of scientific interest, the probability of impact is not large enough to warrant public concern.
  • NEODyS via Tumbling Stone issue #15 on 24 July (quoted headline is no longer present): "First Positive Palermo Scale NEA":
    Asteroid 2002 NT7, a relatively large (H=16) Apollo with a still rather poorly determined orbit, has been on the Risk Pages of both NEODyS and JPL since July 15. . . [For] the first time, the probability of a specific impact of a Near-Earth Asteroid turns out to be larger than that of the "background".
    In discussing both the changing risk monitoring scene and the then-looming concern about 2002 CU11, it was said in issue #12 back in March that Tumbling Stone would be the PR outlet for NEODyS to make announcements such as this above.
  • NASA news page of David Morrison (IAU NEO Working Group Chair, privy to IAU NEO technical review proceedings), "Near-Earth Asteroid (NEA) 2002 NT7" (dated, "Article Posted: July 23, 2002"):
    Asteroid 2002 NT7, a relatively large (H=16) Apollo asteroid with a still rather poorly determined orbit, has been on the Risk Pages of both NEODyS and JPL since July 18. . . The probability of impact is so small that this asteroid remains at a risk level on the Torino scale of 0.
    Fact check: It was well documented and public knowledge that 2002 NT7 went onto the risk pages during 14-15 July, not on the 18th. And NT7 on the 23rd was not at Torino Scale 0 but in fact had been at TS1 for five days straight, visibly so with green highlighting on the JPL Risks page. Furthermore, NT7's Palermo Scale rating on the 23rd was positive for the second day and still climbing at both JPL and NEODyS (peaking, actually, but that wouldn't be known for several days).
  • "Asteroid 2002 NT7: Potential Earth Impact In 2019 Ruled Out," 28 July NASA/JPL NEO Program news item


During the time that A/CC was routinely reporting the rising hazard scale ratings for 2002 NT7, especially as the Palermo Scale rating rose to near 0.0, we kept an eye on the IAU home page for the technical review statement that the IAU and NEO community's policy said would be coming. Instead of having that to report from on 22 July, however, all there was was the fact of the first-ever positive rating for a possible event in current lifetimes, so that's what we reported, and the rest is now history.

What can A/CC do better next time around while covering PHO monitoring in the larger mix of minor object news? From day one, we have had a carefully prepared statement for the media on the A/CC News page, explaining that the A/CC site is media itself and not authoritative, so please consult the cited appropriate authorities, "especially [for] matters concerning Earth impact risks." Since the NT7 uproar, we have also added for the benefit of all readers a clarifying statement that floats in the A/CC News section where we report PHO monitoring. This statement incorporates a link to an article by Jon Giorgini of JPL about understanding how the two risk monitoring sites work, how hazard ratings can change so quickly, and why these ratings shouldn't be of public concern when there has been only a short observing period.

However, those are educational tools available to readers on the A/CC site. So it is also important that A/CC now has a better understanding of how to best present information that might get quoted away from our site. We doubt that a similar news situation will be allowed to develop again, but we're ready if it does.

All this now said, let's return to what we said at the top, that it isn't an A/CC objective to focus on, let alone sensationalize, the impact hazard. We would much prefer to put our resources into reporting about minor objects as stepping stones in the spacefaring legacy that today's pioneers are bequeathing to the coming generations. There just isn't a lot of future in looking to report our destruction.
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