Doubts fail to dent confidence in Israel's Iron Dome
The new United States Defence Secretary, Chuck Hagel, has arrived for his first official trip to Israel, not long after the newly-appointed Secretary of State, John Kerry, last flew out.
During his lengthy nomination process in Washington, Mr Hagel was forced to counter allegations that he did not feel quite the degree of enthusiasm for Israel which is part of the job description for senior American cabinet ministers these days.
Even so when you compare the diplomatic tasks facing President Obama's two point men on foreign policy, it is Mr Hagel who has the easier task here.
To John Kerry, after all, falls the task of breathing life into the moribund peace process between Israel and the Palestinians.
Mr Hagel merely has to demonstrate that security and intelligence cooperation between Israel and the US remains as tight, or tighter, than ever.
It is perhaps not a coincidence that on the eve of his visit, it emerged that the US is preparing to increase its investment in Iron Dome, the missile defence system said by Israel to have shot down nearly 90% of the rockets fired at it from Gaza last November.
That will eventually bring the total American investment in Iron Dome to around $750m - the clearest possible indication that the US government has not been troubled by recent attempts to cast doubt on how well the system works.
To explore those doubts I went to meet Reuven Pedatzur, a former Israeli fighter pilot and strategic studies expert who has been examining the kind of news footage of Iron Dome in action which you can easily find on the Internet.
He believes the pattern of vapour trails you see on screen may not be compatible with the destruction of incoming rockets
Typical pictures show the interceptor missiles streaking into the sky and then the vapour trails twisting and spiralling, apparently as they lock on to the target. There is then an explosion - a successful 'kill', it is generally assumed.
Mr Pedatzur's point is that you cannot necessarily believe the evidence of your own eyes. Not least because your eyes do not provide much real evidence.
For a start the target rockets are too small and too fast-moving to be seen with the naked eye.
And by the time they are over the target zone, their fuel tends to have burned out, leaving them flying on inertia.
"I raise question marks, I don't know exactly what happened but I raise the question marks and I would like to have an answer. I asked the IDF: 'show me your videos, your infra-red videos in which you can see almost everything', but they say it's classified," Mr Pedatzur told me.
"Why it's classified if it's a success, I don't know. If it was a great success, show us it was a great success."
The sceptical questions have generated some publicity here in part because extravagant claims were made for the American Patriot missile system deployed to protect Israel during the Gulf War in 1991 turned out to be wildly over-optimistic.
And anti-missile defence systems have always made some analysts uncomfortable.
That is partly because there is a feeling that any society which found a way to make itself less vulnerable to attack might also be more tempted towards offensive operations.
And partly because the economics of this type of defence strategy just do not seem to add up.
What is the point, runs this line of argument, of firing a $100,000 missile to destroy a home-made rocket that might have cost $50 or less.
Uzi Rubin, who can properly be described as a rocket scientist as former head of the national missile defence programme, is dismissive of the economic argument.
A $50 rocket can cause costly and extensive damage on the ground, he points out, not to mention the risk to human life on which no price can be put.
He says it is perfectly reasonable for Israel to keep detailed infra-red images of Iron Dome at work a closely-guarded secret. Publishing them might help the country's enemies to work out how to evade the system.
And he insists that commonsense tells you that Israelis are right to believe the evidence of their own eyes in this instance.
"You can't fool all the people all the people all the time," Mr Rubin says simply. "This is not the first time that Iron Dome is working, it's the sixth time out. And every time it's working, losses go down, damage goes down and it's obvious for everyone to see."
"I mean you see those rockets going up exploding and no Grad coming down - it's not like in the Gulf War. So by a miracle or something, it's working and people feel safe and rightly so because it's working."
The respected defence writer, Amos Harel, is certainly no tame mouthpiece for Israel's military establishment - but in this case he is inclined to side with the government against its critics.
"I'm no rocket scientist, so I can't explain it in technical terms... but I think these people [the critics] are mostly against the idea of interceptive rocket systems and they're trying to find an argument after it's already been proved that the system is working," he comments.
"It reminds me of those people who argue Nasa never landed on the moon and faked the whole thing at Universal Studios."
In truth, the doubters have failed to dent the confidence of the Israeli military establishment that continues to believe it has a winner in Iron Dome.
And most Israelis seem happy to trust the government on this issue at least.
So while Chuck Hagel will face a timetable of critical meetings on everything from Iran and Syria to the Palestinians and relations with Turkey, the reliability of Iron Dome will be one area of policy at least that will not be troubling him.